Flow resistance in environmental channels: focus on vegetation (original) (raw)

2004, Helsinki University of Technology Water Resources Publications

Abstract

This thesis aims to improve the reliability of the determination of flow resistance in environmentally acceptable channels and floodplains. Special emphasis was placed on addressing the hydraulic effects of vegetation. For this reason, laboratory flume studies with living vegetation were employed. The most notable finding was that, when compared to leafless conditions, the presence of leaves increased the friction factor up to seven-fold. This was strongly dependent on the flow velocity. In addition, the linkage between flow resistance, channel properties, and physical habitat was investigated. For this purpose, field studies were conducted in degraded, restored, and natural channel reaches. To determine friction factor f or Manning’s n for non-submerged woody vegetation, a new procedure based on the measurable characteristics of vegetation and flow was developed. A major advantage of this procedure over the old methods was its ability to estimate the flow resistance of woody vegetation in both leafless and leafy conditions. In determining the velocity profile and flow resistance caused by submerged flexible vegetation, the approach developed by Stephan (2002) was found to be suitable. However, a new formulation was proposed for the shear velocity based on deflected plant height. This modification offered better practical applicability than the original formulation, which requires complicated turbulence measurements. In the field studies, the experimental results for friction factors were, excluding those for low flows, in agreement with the values presented in the literature. Overall, the gathered field data from degraded, restored, and natural channel reaches formed a reference data set, which could be useful in other similar restoration or engineering projects. The field studies showed that both flow resistance and cross-sectional geometry were vital factors in determining local hydraulic conditions. The parameters defining these two factors were found to be simple but nonetheless valuable in evaluating the success of a project which aims to restore local hydraulics. A new procedure for applying the success criteria in the post-project evaluation of local hydraulics was developed.

Figures (61)

Figure 1. Experimental set-up and definition for the coordinate axes (not to scale).

Figure 1. Experimental set-up and definition for the coordinate axes (not to scale).

Figure 3. Test run 010607-21 of series S3Pa with leafy willows and sedges. The average flow velocity was 38.7 cm/s. 2.2 Field studies

Figure 3. Test run 010607-21 of series S3Pa with leafy willows and sedges. The average flow velocity was 38.7 cm/s. 2.2 Field studies

Figure 4. Definition sketch for the used parameters. where S = energy slope and h* = flow depth corresponding to the maximum measured value of the Reynolds stress -u'w’. The definition of u., does not include any plant parameters, whereas the reduced flow cross section caused by the vegetation is included into the definition of u., by means of h-h,,,. From a practical point of view, u., is a convenient definition as h,,, can be easily measured. The definitions of u., and u., are based on both turbulence characteristics and influences of vegetation.

Figure 4. Definition sketch for the used parameters. where S = energy slope and h* = flow depth corresponding to the maximum measured value of the Reynolds stress -u'w’. The definition of u., does not include any plant parameters, whereas the reduced flow cross section caused by the vegetation is included into the definition of u., by means of h-h,,,. From a practical point of view, u., is a convenient definition as h,,, can be easily measured. The definitions of u., and u., are based on both turbulence characteristics and influences of vegetation.

"Note: S3* and R2* refer to the series as a group of nine and eight series, respectively. Table 1. Summary of the experiments. Willow patterns Pa through Pf described in Figure 2.

"Note: S3* and R2* refer to the series as a group of nine and eight series, respectively. Table 1. Summary of the experiments. Willow patterns Pa through Pf described in Figure 2.

Plotting f against Re for the sedges produced a declining curve, but there was considerable deviation in the friction factor corresponding the equivalent Reynolds number (e.g., for Re ~ 24200, f ~ 1.6-2.4; Figure 5a). The same type of plot for leafless willows on bare bottom soil indicated that f was more or less independent of Re (Figure 5d). Combinations of sedges and leafless willows behaved approximately in the same way as only sedges; the values were simply shifted upwards (Figure 5c). Combinations of sedges and leafy willows exhibited he highest f values (Figure 5b). When the different vegetative covers were compared, the series of leafless willows without sedges differed from the rest (Figure 5d). For the leafless willows, the friction factor increased with the depth almost linearly despite the fact that velocity varied by a factor of up to four between the various test runs (I). ee a pee ee ae a zpos 7 ie po

Plotting f against Re for the sedges produced a declining curve, but there was considerable deviation in the friction factor corresponding the equivalent Reynolds number (e.g., for Re ~ 24200, f ~ 1.6-2.4; Figure 5a). The same type of plot for leafless willows on bare bottom soil indicated that f was more or less independent of Re (Figure 5d). Combinations of sedges and leafless willows behaved approximately in the same way as only sedges; the values were simply shifted upwards (Figure 5c). Combinations of sedges and leafy willows exhibited he highest f values (Figure 5b). When the different vegetative covers were compared, the series of leafless willows without sedges differed from the rest (Figure 5d). For the leafless willows, the friction factor increased with the depth almost linearly despite the fact that velocity varied by a factor of up to four between the various test runs (I). ee a pee ee ae a zpos 7 ie po

Table 2. Experimental conditions for test runs 1-9 in series R4 (wheat).

Table 2. Experimental conditions for test runs 1-9 in series R4 (wheat).

It was expected that in the case of submerged flexible prone or waving vegetation f was a function of the relative roughness h,/h. Th agreed well with this, but series S3 behaved somew e results of series R2 and R4 hat differently (Figure 10). As opposed to the grasses and wheat, the sedges were in a staggered pattern not fully covering the bottom. The flexural rigidity of the sed height, and there was a considerable difference in t ges was not constant over the he flexibility of the individual stems, which caused difficulties in determining the deflected plant height. The experiments on series S3 showed that the maximum value of the friction factor was achieved, when the sedges were just submerged (I). For series R+ (wheat), the observed velocity profiles were comparable to typical profiles above flexible plants (Figure 11) exhibiting a reasonably logarithmic shape (III). In Figure 11, velocity was normalised with the shear velocity definition of u., (Equation 12). Because of the ADV limitations, measurements could not be taken in the region of ~6 cm below the water surface. In the region between h,,,, and h,., which denote the minimum and maximum observed deflected plant height, respectively, the flow velocity altered rapidly. Flow characteristics in this region were further investigated by plotting the vertical ordinate z against the corresponding ratio of standard deviation of velocity fluctuations u,,, to average velocity u. The value of this ratio was small and almost constant in the non-vegetated cross-section, but increased significantly at the level of the plant tips (III). The maximum values of the turbulence intensity u,,, and Reynolds stress —u'w’ were recorded at approximately h above the mean deflected height (Figure 12). i.e. slightly pup?

It was expected that in the case of submerged flexible prone or waving vegetation f was a function of the relative roughness h,/h. Th agreed well with this, but series S3 behaved somew e results of series R2 and R4 hat differently (Figure 10). As opposed to the grasses and wheat, the sedges were in a staggered pattern not fully covering the bottom. The flexural rigidity of the sed height, and there was a considerable difference in t ges was not constant over the he flexibility of the individual stems, which caused difficulties in determining the deflected plant height. The experiments on series S3 showed that the maximum value of the friction factor was achieved, when the sedges were just submerged (I). For series R+ (wheat), the observed velocity profiles were comparable to typical profiles above flexible plants (Figure 11) exhibiting a reasonably logarithmic shape (III). In Figure 11, velocity was normalised with the shear velocity definition of u., (Equation 12). Because of the ADV limitations, measurements could not be taken in the region of ~6 cm below the water surface. In the region between h,,,, and h,., which denote the minimum and maximum observed deflected plant height, respectively, the flow velocity altered rapidly. Flow characteristics in this region were further investigated by plotting the vertical ordinate z against the corresponding ratio of standard deviation of velocity fluctuations u,,, to average velocity u. The value of this ratio was small and almost constant in the non-vegetated cross-section, but increased significantly at the level of the plant tips (III). The maximum values of the turbulence intensity u,,, and Reynolds stress —u'w’ were recorded at approximately h above the mean deflected height (Figure 12). i.e. slightly pup?

Figure 11. Averaged profiles for velocity normalised with the shear velocity u., and flow depth h for wheat (R+). The dashed line denotes the mean deflected plant height. See Table 2 for test run description.

Figure 11. Averaged profiles for velocity normalised with the shear velocity u., and flow depth h for wheat (R+). The dashed line denotes the mean deflected plant height. See Table 2 for test run description.

= Measured velocity profiles for the experiments carried out with wheat were described well by the approach developed by Stephan (2002) indicating that it could be applied beyond the original scope (highly flexible aquatic vegetation). The approach was a suitable method for determining velocity profile and flow resistance (by Equation 8) for a wide range of submerged vegetation from highly flexible aquatic plants to wheat. Introducing the simple definition of u., (Equation 12), which was determined using the flow layer above the mean deflected plant height, yielded good results for the comparison of measured and calculated velocity profiles. Similar results were obtained with the definition of u., (Equation 13), which included data from the turbulence measurements. However, u., was a convenient definition for the shear velocity as the mean deflected plant height h,, can be easily measured. Consequently, for determining the friction factor, Equations 8 and 10 were modified to use the definition of u.,, which did not require complicated turbulence measurements and was considered straightforward to apply within a numerical modelling framework (III).

= Measured velocity profiles for the experiments carried out with wheat were described well by the approach developed by Stephan (2002) indicating that it could be applied beyond the original scope (highly flexible aquatic vegetation). The approach was a suitable method for determining velocity profile and flow resistance (by Equation 8) for a wide range of submerged vegetation from highly flexible aquatic plants to wheat. Introducing the simple definition of u., (Equation 12), which was determined using the flow layer above the mean deflected plant height, yielded good results for the comparison of measured and calculated velocity profiles. Similar results were obtained with the definition of u., (Equation 13), which included data from the turbulence measurements. However, u., was a convenient definition for the shear velocity as the mean deflected plant height h,, can be easily measured. Consequently, for determining the friction factor, Equations 8 and 10 were modified to use the definition of u.,, which did not require complicated turbulence measurements and was considered straightforward to apply within a numerical modelling framework (III).

Figure 14. The principle of the Strahler ordering scheme applied to a woody plant. scheme to trees (Figure 14). McMahon and Kronauer (1976) showed that the branching pattern within any tree species is approximately sta means that the structure is self-similar, and any patch of the s of the entire tree. Furthermore, they conclude that the prince design is the maintenance of elastic similarity, and for elastic the diameters are proportional to the 3/2 power of their leng TUC iple ally h. 1 ionary, which ure is a model of mechanical similar beams, hey presented three equations of branching, diameter, and length ratio that are based on the geomorphic laws of drainage network composition by H orto n (1945) and Schumm (1956). In the present study, a new application for his knowledge was proposed, namely the determination of the projected area of a branched plant.

Figure 14. The principle of the Strahler ordering scheme applied to a woody plant. scheme to trees (Figure 14). McMahon and Kronauer (1976) showed that the branching pattern within any tree species is approximately sta means that the structure is self-similar, and any patch of the s of the entire tree. Furthermore, they conclude that the prince design is the maintenance of elastic similarity, and for elastic the diameters are proportional to the 3/2 power of their leng TUC iple ally h. 1 ionary, which ure is a model of mechanical similar beams, hey presented three equations of branching, diameter, and length ratio that are based on the geomorphic laws of drainage network composition by H orto n (1945) and Schumm (1956). In the present study, a new application for his knowledge was proposed, namely the determination of the projected area of a branched plant.

Fig. 2. Spacing of willows in the set-ups Pa, Pb, Pd, Pe and Pf. Figures show only half (3 m) of the 6 m long test area (not to scale). Series group S3° (sedges—willows). Natural yet nursery-grown slender tufted-sedges (Carex acuta) were placed in the natural floodplain topsoil layer by boring holes for the planting pots (diameter 4 cm). Otherwise, the natural root structure and soil compac- tion were left intact. The sedges were positioned in a staggered pattern averaging 512 stems/m*. In each plant pot there were several stems of 3 mm in average diameter. In the pots, the stems were randomly in clusters or apart; usually the diameter of the stems as a group was ~ 20 mm. The lower part of the stems up to the height of ~5cm was more or less stiff. The average height of the sedges was approximately 30cm. The maximum stem length was kept at 35 cm by cutting. The willows (Salix sp.) averaged Series group R2™ (grasses—willows). The veg- etation boxes were filled in the field with a 10-cm thick natural floodplain topsoil layer growing mixed grasses. The length of the grasses was in average 30cm with the individual stem length ranging between 20 and 40 cm. When visually observed, the grass cover was relatively homogeneous, but spatial analysis of dry biomass in the vegetation boxes revealed up to 35% variations from the average (130 g/m’, dried 1.5 h in 105 °C). In series R2”, only leafless willows were used. The willows were installed in five various patterns with the grasses

Fig. 2. Spacing of willows in the set-ups Pa, Pb, Pd, Pe and Pf. Figures show only half (3 m) of the 6 m long test area (not to scale). Series group S3° (sedges—willows). Natural yet nursery-grown slender tufted-sedges (Carex acuta) were placed in the natural floodplain topsoil layer by boring holes for the planting pots (diameter 4 cm). Otherwise, the natural root structure and soil compac- tion were left intact. The sedges were positioned in a staggered pattern averaging 512 stems/m*. In each plant pot there were several stems of 3 mm in average diameter. In the pots, the stems were randomly in clusters or apart; usually the diameter of the stems as a group was ~ 20 mm. The lower part of the stems up to the height of ~5cm was more or less stiff. The average height of the sedges was approximately 30cm. The maximum stem length was kept at 35 cm by cutting. The willows (Salix sp.) averaged Series group R2™ (grasses—willows). The veg- etation boxes were filled in the field with a 10-cm thick natural floodplain topsoil layer growing mixed grasses. The length of the grasses was in average 30cm with the individual stem length ranging between 20 and 40 cm. When visually observed, the grass cover was relatively homogeneous, but spatial analysis of dry biomass in the vegetation boxes revealed up to 35% variations from the average (130 g/m’, dried 1.5 h in 105 °C). In series R2”, only leafless willows were used. The willows were installed in five various patterns with the grasses

Fig. 3. Test run 010607-21 of series S3_Pa with willows and sedges. The average flow velocity is 38.7 cm/s. 4. Experimental results Due to the physical nature of the experimental set-up the flow was gradually varied. At the beginning of the test area there was an abrupt change in roughness, which introduces transition into the flow. However, a new equilibrium was developed and a declining surface profile with a constant slope was produced for part of the test area. Flow resistance was determined by measuring head oss and then calculating the friction factor, f, from the energy loss, H;, using Bernoulli’s Eq. (1) and the Darcy—Weisbach Eq. (2). Both potential and velocity heads were incorporated in the calcu- ations. The validity of this approach was checked by applying a momentum equation including pressure, velocity, and drag terms for channe bottom soil, glass walls, and vegetation. The drag contributed by the glass walls was negligible. By conducting experiments without any vegetation the average base friction factor for the test section (bottom and walls) was determined to be 0.055 and 0.061 for series S3“ and R2*, respectively. For further analysis, the base friction factor of the bottom and walls was subtracted from the results given by Eq. (2). For simplicity, the base friction

Fig. 3. Test run 010607-21 of series S3_Pa with willows and sedges. The average flow velocity is 38.7 cm/s. 4. Experimental results Due to the physical nature of the experimental set-up the flow was gradually varied. At the beginning of the test area there was an abrupt change in roughness, which introduces transition into the flow. However, a new equilibrium was developed and a declining surface profile with a constant slope was produced for part of the test area. Flow resistance was determined by measuring head oss and then calculating the friction factor, f, from the energy loss, H;, using Bernoulli’s Eq. (1) and the Darcy—Weisbach Eq. (2). Both potential and velocity heads were incorporated in the calcu- ations. The validity of this approach was checked by applying a momentum equation including pressure, velocity, and drag terms for channe bottom soil, glass walls, and vegetation. The drag contributed by the glass walls was negligible. By conducting experiments without any vegetation the average base friction factor for the test section (bottom and walls) was determined to be 0.055 and 0.061 for series S3“ and R2*, respectively. For further analysis, the base friction factor of the bottom and walls was subtracted from the results given by Eq. (2). For simplicity, the base friction

Summary of the experiments Note: S3* and R2* refer to the series as a group of seven and eight series, respectively. Table 1 willows bent at high discharges with large inundation resulting in a maximum reduction of willow height by 10 cm. The grasses were very flexible and formed a wavy surface. After each day of experiments the grasses were found lying on the flume bottom with the combed appearance which is commonly seen in nature after floods. against Re for the sedges overall produces a nice declining curve, but there is considerable deviation in the friction factor corresponding the equivalent Re (e.g. for Re ~ 24,200;f ~ 1.6-2.4, Fig. 4a). The same type of plot for leafless willows on bare bottom soil indicates that fis more or less independent of Re (Fig. 4d). Combinations of sedges and leafless willows behave approximately in the same way as only sedges; the values are just shifted upwards (Fig. 4c). It should be noted that the frontal area of the eafless willows is relatively small. Combinations of sedges and leafy willows give the highest values of f, and produce the most scattered plot, but distinctive patterns are found, when the data are classified according to the flow depth (Fig. 4b). Interestingly, eaves on willows seemed to double or even triple the friction factor compared to the leafless case despite the fact that the bottom was growing sedges in both cases.

Summary of the experiments Note: S3* and R2* refer to the series as a group of seven and eight series, respectively. Table 1 willows bent at high discharges with large inundation resulting in a maximum reduction of willow height by 10 cm. The grasses were very flexible and formed a wavy surface. After each day of experiments the grasses were found lying on the flume bottom with the combed appearance which is commonly seen in nature after floods. against Re for the sedges overall produces a nice declining curve, but there is considerable deviation in the friction factor corresponding the equivalent Re (e.g. for Re ~ 24,200;f ~ 1.6-2.4, Fig. 4a). The same type of plot for leafless willows on bare bottom soil indicates that fis more or less independent of Re (Fig. 4d). Combinations of sedges and leafless willows behave approximately in the same way as only sedges; the values are just shifted upwards (Fig. 4c). It should be noted that the frontal area of the eafless willows is relatively small. Combinations of sedges and leafy willows give the highest values of f, and produce the most scattered plot, but distinctive patterns are found, when the data are classified according to the flow depth (Fig. 4b). Interestingly, eaves on willows seemed to double or even triple the friction factor compared to the leafless case despite the fact that the bottom was growing sedges in both cases.

Fig. 4. Friction factor vs. Reynolds number (a—d) and flow depth (e—h) for series S3* (see Table 1 for series description). Data are classified according to the entrance flow depth, io, and flow velocity, respectively.

Fig. 4. Friction factor vs. Reynolds number (a—d) and flow depth (e—h) for series S3* (see Table 1 for series description). Data are classified according to the entrance flow depth, io, and flow velocity, respectively.

Fig. 5. Friction factor vs. Reynolds number for series R2* (see Table 1 for series description). Data are classified according to the entrance flo’ depth, /o.

Fig. 5. Friction factor vs. Reynolds number for series R2* (see Table 1 for series description). Data are classified according to the entrance flo’ depth, /o.

Fig. 6. Comparison of series R2 (grasses) and S3 (sedges): fitted curves f vs. Re (left) and f vs. k/h (right).

Fig. 6. Comparison of series R2 (grasses) and S3 (sedges): fitted curves f vs. Re (left) and f vs. k/h (right).

two different patterns (Fig. 1) with the sedges. The willows were investigated first with leaves and in the next phase without leaves. In the last phase the sedges were removed, and the leafless willows on bare bottom soil were investigated.

two different patterns (Fig. 1) with the sedges. The willows were investigated first with leaves and in the next phase without leaves. In the last phase the sedges were removed, and the leafless willows on bare bottom soil were investigated.

Figure 2. Vegetal drag coefficient as a function of the corresponding depth Reynolds number. Data are classified according to th flow depth, 4». Willow patterns Pa and Pf described in Figure 1. Note vertical scale.

Figure 2. Vegetal drag coefficient as a function of the corresponding depth Reynolds number. Data are classified according to th flow depth, 4». Willow patterns Pa and Pf described in Figure 1. Note vertical scale.

Figure 3. Four examples of the dependence between the pro- jected area of the leafless willows and the flow depth.

Figure 3. Four examples of the dependence between the pro- jected area of the leafless willows and the flow depth.

Figure 4. Measured and predicted drag coefficient vs. the Rey- nolds number based on the characteristic diameter. Constant line of Cy = 1.5 used in Mertens’ and Nuding’s methods is shown for reference.

Figure 4. Measured and predicted drag coefficient vs. the Rey- nolds number based on the characteristic diameter. Constant line of Cy = 1.5 used in Mertens’ and Nuding’s methods is shown for reference.

Figure 5. Presence of leaves affects significantly the flow resis- tance. Friction factor vs. the relative submergence for leafy and leafless willows (pattern Pa). The dashed line separates the leafless and leafy cases.

Figure 5. Presence of leaves affects significantly the flow resis- tance. Friction factor vs. the relative submergence for leafy and leafless willows (pattern Pa). The dashed line separates the leafless and leafy cases.

where «= von Karman constant, k, = equivalent sand roughness, and C = integration constant. Integration of Eq. 2 yields the mean velocity U. where « = 0.4 and hp» = mean deflected height of vegetation (definitions in Figure 1). Based on flume experiments with three species of highly flexible aquatic vegetation it was concluded that the log profile well described the velocity profile above the plants. The mean deflected height described the hydraulic roughness of the plants by summarising the plant and

where «= von Karman constant, k, = equivalent sand roughness, and C = integration constant. Integration of Eq. 2 yields the mean velocity U. where « = 0.4 and hp» = mean deflected height of vegetation (definitions in Figure 1). Based on flume experiments with three species of highly flexible aquatic vegetation it was concluded that the log profile well described the velocity profile above the plants. The mean deflected height described the hydraulic roughness of the plants by summarising the plant and

* R4 = wheat; S3 = sedges; RP1 = leafy willows with grasses *See Eq. 6 for definitions Table 1. Experimental conditions.

* R4 = wheat; S3 = sedges; RP1 = leafy willows with grasses *See Eq. 6 for definitions Table 1. Experimental conditions.

Figure 2. Experimental set-up and definition for the coordinate axes (not to scale).

Figure 2. Experimental set-up and definition for the coordinate axes (not to scale).

For wheat, velocity profiles were measured at three longitudinal locations (x = 3.5, 3.65 ani 3.8 m) to investigate possible effects of non-uniformity on the longitudinal development c the velocity profile. Relative submergence h/h,,, ranged from 1.5 to 3.3 for this set o measurements. It was found that for each test run the three vertical velocity profiles wer almost identical, though scatter was evident because of natural variability in the roughnes cover. Here, a simple spatial averaging procedure was introduced because of the insufficier number of profiles for the double averaging technique described by e.g. Nikora et al. (2001. For the streamwise velocity u, the point measurements of the three measured profiles wer averaged for a given distance from the bed z (Figure 3). Averages for the turbulence intensit Urs (Figure 4, left) and the Reynolds stress —u'w’ (Figure 4, right) were calculated with th same averaging procedure.

For wheat, velocity profiles were measured at three longitudinal locations (x = 3.5, 3.65 ani 3.8 m) to investigate possible effects of non-uniformity on the longitudinal development c the velocity profile. Relative submergence h/h,,, ranged from 1.5 to 3.3 for this set o measurements. It was found that for each test run the three vertical velocity profiles wer almost identical, though scatter was evident because of natural variability in the roughnes cover. Here, a simple spatial averaging procedure was introduced because of the insufficier number of profiles for the double averaging technique described by e.g. Nikora et al. (2001. For the streamwise velocity u, the point measurements of the three measured profiles wer averaged for a given distance from the bed z (Figure 3). Averages for the turbulence intensit Urs (Figure 4, left) and the Reynolds stress —u'w’ (Figure 4, right) were calculated with th same averaging procedure.

Figure 4. Averaged profiles for turbulence intensity (left) and Reynolds stress (right) for experiments with wheat. vegetation (e.g. Tsujimoto et al. 1992, Ikeda and Kanazawa 1996). In the present study, the maximum values for un; and —u'w' were recorded at approximately hp yp, i.e. slightly above the mean deflected height (Figure 4). No relation between the maximums of us; and the corresponding l/h, , could be found.

Figure 4. Averaged profiles for turbulence intensity (left) and Reynolds stress (right) for experiments with wheat. vegetation (e.g. Tsujimoto et al. 1992, Ikeda and Kanazawa 1996). In the present study, the maximum values for un; and —u'w' were recorded at approximately hp yp, i.e. slightly above the mean deflected height (Figure 4). No relation between the maximums of us; and the corresponding l/h, , could be found.

Velocity profiles were measured at three longitudinal locations (« = 0.9, 1.5 and 5.5 m) to examine the longitudinal development of the velocity profiles. Several measurements were taken close to the bottom to examine the possible effects of uneven natural floodplain soil. In addition, four lateral locations were recorded for x = 5.5 m to examine the influence of the staggered plant pattern. Relative submergence h/h,», was 1.4—2.3. Figure 5 shows velocity profiles and Figure 6 the corresponding profiles of um; and —u'w' for the position x = 5.5 m and y = 0.55 m.

Velocity profiles were measured at three longitudinal locations (« = 0.9, 1.5 and 5.5 m) to examine the longitudinal development of the velocity profiles. Several measurements were taken close to the bottom to examine the possible effects of uneven natural floodplain soil. In addition, four lateral locations were recorded for x = 5.5 m to examine the influence of the staggered plant pattern. Relative submergence h/h,», was 1.4—2.3. Figure 5 shows velocity profiles and Figure 6 the corresponding profiles of um; and —u'w' for the position x = 5.5 m and y = 0.55 m.

Figure 6. Plots of turbulence intensity (left) and Reynolds stress (right) for the sedges. rigidity of the sedges was not constant over the height, and there was a considerable difference in the flexibility of the individual stems. Furthermore, an abrupt roughness could be observed at the transition between test section and gravel bed change in . The flow gradually decelerated inside the vegetation and accelerated above it. As expected, the longitudinal and lateral differences in the profiles were far more significant than in case of denser vegetation due to the staggered plant pattern. For example, the shape of the velocity profile inside the vegetation changes notably at the downstream location x = 5.5 m as U and h/h, increase (Figure 5). In S3-1 the flow appears to be dominated by vegetal drag, a stronger shear layer is apparent and turbulent stress from the non-vegetated part o but in $3-2 f the cross- section contribute momentum to the flow inside the vegetation (Figure 6). For S3-3, the lowest points could not measured because of the waving vegetation.

Figure 6. Plots of turbulence intensity (left) and Reynolds stress (right) for the sedges. rigidity of the sedges was not constant over the height, and there was a considerable difference in the flexibility of the individual stems. Furthermore, an abrupt roughness could be observed at the transition between test section and gravel bed change in . The flow gradually decelerated inside the vegetation and accelerated above it. As expected, the longitudinal and lateral differences in the profiles were far more significant than in case of denser vegetation due to the staggered plant pattern. For example, the shape of the velocity profile inside the vegetation changes notably at the downstream location x = 5.5 m as U and h/h, increase (Figure 5). In S3-1 the flow appears to be dominated by vegetal drag, a stronger shear layer is apparent and turbulent stress from the non-vegetated part o but in $3-2 f the cross- section contribute momentum to the flow inside the vegetation (Figure 6). For S3-3, the lowest points could not measured because of the waving vegetation.

Applying the approach of Stephan (2001) was straightforward and produced in overall good results. Largest discrepancies between the measured and predicted profiles were related to the higher discharges with larger relative submergence h/h,,». Measured and predicted velocities are compared in Figure 7 for u«2 (left) and u+3 (right), which gave the best results. Similar analysis of the data with u., and u., showed major discrepancies. The corresponding plots are not shown here. Applying the approach of Carollo et al. (2002) revealed major problems. With the present data, Eq. 5 returned unrealistic values. It can only be concluded that the semi-empirical parameters in the equations depend on the boundary conditions of the experiments of Carollo et al. It appears that the approach is strongly scale dependent and that differences in the experimental set up are responsible for its inapplicability in this study.

Applying the approach of Stephan (2001) was straightforward and produced in overall good results. Largest discrepancies between the measured and predicted profiles were related to the higher discharges with larger relative submergence h/h,,». Measured and predicted velocities are compared in Figure 7 for u«2 (left) and u+3 (right), which gave the best results. Similar analysis of the data with u., and u., showed major discrepancies. The corresponding plots are not shown here. Applying the approach of Carollo et al. (2002) revealed major problems. With the present data, Eq. 5 returned unrealistic values. It can only be concluded that the semi-empirical parameters in the equations depend on the boundary conditions of the experiments of Carollo et al. It appears that the approach is strongly scale dependent and that differences in the experimental set up are responsible for its inapplicability in this study.

Figure | The principle of the Strahler ordering scheme applied to a woody plant. where N is the number of segments in a particular order, d is the average diameter within an order, and L is the average length within an order. Rg describes how many branches of order m a bigger branch of order m + 1 supports. Similarly, Rp and R_, describe the corresponding differences in branch thickness and length, respectively. The equations are based on the geomor- phic laws of drainage network composition by Horton (1945) and

Figure | The principle of the Strahler ordering scheme applied to a woody plant. where N is the number of segments in a particular order, d is the average diameter within an order, and L is the average length within an order. Rg describes how many branches of order m a bigger branch of order m + 1 supports. Similarly, Rp and R_, describe the corresponding differences in branch thickness and length, respectively. The equations are based on the geomor- phic laws of drainage network composition by Horton (1945) and

Figure 2. Predicted and measured friction factors, velocities and unit discharges for two patterns of leafless willows. See text for the definition of th efficiency Reg. The dashed line denotes the perfect agreement. Table 3 Parameter values used in com- puting the projected area for the leafless willows. In the case of the leafless willows, testing follows the steps presented in Section 3.2.2. Values for the plant structure para- meters Rg and Rp were taken from the poplar data (Table 1) as measured data were not available for the willows. R; was computed from Rp using Eq. (8). Values for dinin, dhigh, H and Lhigh Were estimated from the plant specimens. The number of segments in the highest order, Nin high, WaS One. The values of the parameters are collected in Table 3. The resulting number of

Figure 2. Predicted and measured friction factors, velocities and unit discharges for two patterns of leafless willows. See text for the definition of th efficiency Reg. The dashed line denotes the perfect agreement. Table 3 Parameter values used in com- puting the projected area for the leafless willows. In the case of the leafless willows, testing follows the steps presented in Section 3.2.2. Values for the plant structure para- meters Rg and Rp were taken from the poplar data (Table 1) as measured data were not available for the willows. R; was computed from Rp using Eq. (8). Values for dinin, dhigh, H and Lhigh Were estimated from the plant specimens. The number of segments in the highest order, Nin high, WaS One. The values of the parameters are collected in Table 3. The resulting number of

Figure 3 Design situation 1: Predicted and measured friction factors (left), mean velocities (mid) and unit discharges (right) for leafy willows. See text for the definition of the efficiency Rer. The dashed line denotes the perfect agreement.

Figure 3 Design situation 1: Predicted and measured friction factors (left), mean velocities (mid) and unit discharges (right) for leafy willows. See text for the definition of the efficiency Rer. The dashed line denotes the perfect agreement.

Figure 4 Design situation 2: Predicted and measured friction factors (left), mean velocities (mid) and flow depths (right) for leafy willows. The dashed line denotes the perfect agreement.

Figure 4 Design situation 2: Predicted and measured friction factors (left), mean velocities (mid) and flow depths (right) for leafy willows. The dashed line denotes the perfect agreement.

Fig. 1. Before and after the restoration: the brook was restored to its historical meandering channel (right) from the channelized reach, which was dredged in the 1960’s (left). The restoration project included design challenges, such as reconstruction of meanders, cohesive sediments, mild slopes, diverse vegetation, and harsh climatic conditions (Fig. 1). Because of relatively low stream power and cohesive sediments, natural geomorphological processes can be slow. Thus, channel instabilities may not be a problem, but neither are the defects in channel design adjusted by changes in the channel morphology. The boreal climate with a short growing season and a cold winter restricts both bioengineering and natural recovery of vegetation. In addition, privately owned lands in the brook valley set spatial boundary conditions for the hydraulic and geomorphic design. The brook provides several interesting field study sites as both pristine and engineered reaches of various levels of disturbance or degradation can be found.

Fig. 1. Before and after the restoration: the brook was restored to its historical meandering channel (right) from the channelized reach, which was dredged in the 1960’s (left). The restoration project included design challenges, such as reconstruction of meanders, cohesive sediments, mild slopes, diverse vegetation, and harsh climatic conditions (Fig. 1). Because of relatively low stream power and cohesive sediments, natural geomorphological processes can be slow. Thus, channel instabilities may not be a problem, but neither are the defects in channel design adjusted by changes in the channel morphology. The boreal climate with a short growing season and a cold winter restricts both bioengineering and natural recovery of vegetation. In addition, privately owned lands in the brook valley set spatial boundary conditions for the hydraulic and geomorphic design. The brook provides several interesting field study sites as both pristine and engineered reaches of various levels of disturbance or degradation can be found.

Fig. 2. Variation of friction factor and discharge in different years and seasons in reaches M3, M6 and M7. not limited to the bankfull stage or the dominant discharge, and the data are biased towards small discharges. Variation of discharges can be seen in Fig. 2, where reaches M3, M6 and M7 represent degraded, pristine and restored reaches, respectively.

Fig. 2. Variation of friction factor and discharge in different years and seasons in reaches M3, M6 and M7. not limited to the bankfull stage or the dominant discharge, and the data are biased towards small discharges. Variation of discharges can be seen in Fig. 2, where reaches M3, M6 and M7 represent degraded, pristine and restored reaches, respectively.

* See text for definitions Vegetation can be a major source of temporal variation in flow resistance. Dense vegetation can also alter the effective area of a cross section that conveys the flow. Considerable seasonal variation caused by the growth of vegetation has been reported by several authors including Bakry et al. (1992), Fisher (1995), Sellin and van Beesten (2002) and Maione et al. (2000). Vegetative characteristics in boreal streams can be expected to be different compared to warmer climates. In the present study, temporal variation in flow resistance was investigated in reaches with the greatest number of measurements: M3, M6 and M7. Data available for the analysis covered years 1997-2001, but measurements were

* See text for definitions Vegetation can be a major source of temporal variation in flow resistance. Dense vegetation can also alter the effective area of a cross section that conveys the flow. Considerable seasonal variation caused by the growth of vegetation has been reported by several authors including Bakry et al. (1992), Fisher (1995), Sellin and van Beesten (2002) and Maione et al. (2000). Vegetative characteristics in boreal streams can be expected to be different compared to warmer climates. In the present study, temporal variation in flow resistance was investigated in reaches with the greatest number of measurements: M3, M6 and M7. Data available for the analysis covered years 1997-2001, but measurements were

Fig. 3. Reach-averaged friction factor, f, as a function of the corresponding Reynolds number. Because of the scaling, f values greater than five are not shown. sectional geometry, the statistical analysis showed no clear dependency between the parameters (Fig 5). However, clear differences were detected between the reaches. With equal values of v, the depth width ratio was clearly higher in reach M7 than in reaches M6 and M8.

Fig. 3. Reach-averaged friction factor, f, as a function of the corresponding Reynolds number. Because of the scaling, f values greater than five are not shown. sectional geometry, the statistical analysis showed no clear dependency between the parameters (Fig 5). However, clear differences were detected between the reaches. With equal values of v, the depth width ratio was clearly higher in reach M7 than in reaches M6 and M8.

Fig. 4. Depth-width ratio vs. friction factor for sub-reaches of M3, M6, M7 and MS. See text for the statistical parameters R? and p.

Fig. 4. Depth-width ratio vs. friction factor for sub-reaches of M3, M6, M7 and MS. See text for the statistical parameters R? and p.

Fig. 5. Depth-width ratio vs. average velocity for sub-reaches of M3, M6, M7 and M6é. See text for the statistical parameters R? and p.

Fig. 5. Depth-width ratio vs. average velocity for sub-reaches of M3, M6, M7 and M6é. See text for the statistical parameters R? and p.

Fig. 6. Procedure for applying the success criteria in post-project evaluation of local hydraulics. These criteria can be used as an assessment tool in post-project evaluation. Application of this procedure is presented in Fig. 6. For both the reference reach and the restored reach, the flow velocity is plotted versus 1) the friction factor, and 2) the parameter(s) of cross-sectional geometry. The plots are compared to investigate if the relationships are similar for the reference reach and the restored reach. An example of applying the procedure is shown in Fig. 7.

Fig. 6. Procedure for applying the success criteria in post-project evaluation of local hydraulics. These criteria can be used as an assessment tool in post-project evaluation. Application of this procedure is presented in Fig. 6. For both the reference reach and the restored reach, the flow velocity is plotted versus 1) the friction factor, and 2) the parameter(s) of cross-sectional geometry. The plots are compared to investigate if the relationships are similar for the reference reach and the restored reach. An example of applying the procedure is shown in Fig. 7.

Fig. 7. An example application of the procedure: a) Depth-width ratio vs. flow velocity differs in reach M7 from reference reach Mo. b) Friction factors vs. flow velocities match relatively well.

Fig. 7. An example application of the procedure: a) Depth-width ratio vs. flow velocity differs in reach M7 from reference reach Mo. b) Friction factors vs. flow velocities match relatively well.

Tuusulanjoki A sensitivity analysis was carried out for the measurements. An error of 10%-20% in discharge was estimated resulting from errors in the velocity measurement procedure (National Board of Waters 1984). Maximum errors in the cross-sectional coordinate measurements were considered Dx = Dy = 10 cm and in location of cross section DL = 2 m. The changes in the cross sections due to erosion and sedimentation were considered negligible in the limits of the sensitivity analysis, because the soil is mainly cohesive in both rivers. The very mild longitu- dinal slopes caused uncertainty in water surface slope measurements. The associated error in the water level measurement was considered to be Dh=2 cm.

Tuusulanjoki A sensitivity analysis was carried out for the measurements. An error of 10%-20% in discharge was estimated resulting from errors in the velocity measurement procedure (National Board of Waters 1984). Maximum errors in the cross-sectional coordinate measurements were considered Dx = Dy = 10 cm and in location of cross section DL = 2 m. The changes in the cross sections due to erosion and sedimentation were considered negligible in the limits of the sensitivity analysis, because the soil is mainly cohesive in both rivers. The very mild longitu- dinal slopes caused uncertainty in water surface slope measurements. The associated error in the water level measurement was considered to be Dh=2 cm.

Table 1. Summary of the field data of the Tuusulanjoki (T) and Pantaneenjoki (P); reach-averaged values. and some local losses caused by collapsed banks in the mid-reach. The summary of the results is presented in Table 1 and in Fig. 4. Significant changes in friction factors caused by vegetation growth were not detected during the growing season, whereas some yearly differences were found. The seasonal and yearly variation and the dates of measurements are given in Fig. 5. For

Table 1. Summary of the field data of the Tuusulanjoki (T) and Pantaneenjoki (P); reach-averaged values. and some local losses caused by collapsed banks in the mid-reach. The summary of the results is presented in Table 1 and in Fig. 4. Significant changes in friction factors caused by vegetation growth were not detected during the growing season, whereas some yearly differences were found. The seasonal and yearly variation and the dates of measurements are given in Fig. 5. For

Fig. 4. Darcy-Weisbach friction factor fand Manning resistance coefficient n as a function of Reynolds number Re in the Tuusulanjoki (T) and Pantaneenjoki (P); reach-averaged results.

Fig. 4. Darcy-Weisbach friction factor fand Manning resistance coefficient n as a function of Reynolds number Re in the Tuusulanjoki (T) and Pantaneenjoki (P); reach-averaged results.

Fig. 5. Yearly and seasonal variation of friction factor and discharge in the Tuusulanjoki (T) and Pantaneenjoki (P).

Fig. 5. Yearly and seasonal variation of friction factor and discharge in the Tuusulanjoki (T) and Pantaneenjoki (P).

(NQ) to mean high discharge (MHQ). The sur- face width varied from 3 m to about 25 m. In the approach to compute f, it was assumed that reach P2 after the construction can be treated similarly to the other reaches despite the narrow flood- plains constructed above the mean water level. At the same water levels, the ratio of the wetted perimeter to the cross-sectional area did not significantly change from the pre-construction state. Therefore, the channel was not treated as a typical two-stage channel. The introduced error is expected to be small for high flows, which are important for flood conveyance.

(NQ) to mean high discharge (MHQ). The sur- face width varied from 3 m to about 25 m. In the approach to compute f, it was assumed that reach P2 after the construction can be treated similarly to the other reaches despite the narrow flood- plains constructed above the mean water level. At the same water levels, the ratio of the wetted perimeter to the cross-sectional area did not significantly change from the pre-construction state. Therefore, the channel was not treated as a typical two-stage channel. The introduced error is expected to be small for high flows, which are important for flood conveyance.

Fig. 7. Darcy-Weisbach friction factor f as a function of discharge Q (m° s~') in sub-reaches of reach P2 of the Pantaneenjoki; results are presented for each sub-reach between two cross sections. BOREAL ENV. RES. Vol.9 * Hydraulics of environmental flood management

Fig. 7. Darcy-Weisbach friction factor f as a function of discharge Q (m° s~') in sub-reaches of reach P2 of the Pantaneenjoki; results are presented for each sub-reach between two cross sections. BOREAL ENV. RES. Vol.9 * Hydraulics of environmental flood management

Table 2. Darcy-Weisbach friction factor f partitioned by Eq. 5; f, includes the effects of the channel shape. Reach- averaged values for two discharges. A sensitivity analysis was carried out for the computation procedure. Partial derivatives of Eq. 3 were determined to get the error in f due to errors in the measured parameters of cross sec- tion, velocity and water level. Unsteadiness of the flow was not of particular concern during the measurements as the catchment is mostly forest and fields, and the slopes are mild. Based on

Table 2. Darcy-Weisbach friction factor f partitioned by Eq. 5; f, includes the effects of the channel shape. Reach- averaged values for two discharges. A sensitivity analysis was carried out for the computation procedure. Partial derivatives of Eq. 3 were determined to get the error in f due to errors in the measured parameters of cross sec- tion, velocity and water level. Unsteadiness of the flow was not of particular concern during the measurements as the catchment is mostly forest and fields, and the slopes are mild. Based on

first winter because of extreme winter conditions with up to 1.6-metre-thick ice cover. Success of bioengineering methods is highly dependent on weather conditions during the first couple of years. Re-installation and re-planting may be needed during the first years after the construc- tion works. After the construction of reach P2, friction factors were still relatively high during low flows because only minor clearing was per- formed in the lower part of the cross-section. The tested bioengineering methods had no significant effect on the flow resistance, and therefore their use did not reduce the conveyance capacity of the channel. The application of bioengineering methods in the Pantaéneenjoki proved to be rela- tively successful. However, some of the tested bioengineering methods were unsuccessful, as many live stakes and fascines died during the

first winter because of extreme winter conditions with up to 1.6-metre-thick ice cover. Success of bioengineering methods is highly dependent on weather conditions during the first couple of years. Re-installation and re-planting may be needed during the first years after the construc- tion works. After the construction of reach P2, friction factors were still relatively high during low flows because only minor clearing was per- formed in the lower part of the cross-section. The tested bioengineering methods had no significant effect on the flow resistance, and therefore their use did not reduce the conveyance capacity of the channel. The application of bioengineering methods in the Pantaéneenjoki proved to be rela- tively successful. However, some of the tested bioengineering methods were unsuccessful, as many live stakes and fascines died during the

Loading...

Loading Preview

Sorry, preview is currently unavailable. You can download the paper by clicking the button above.

References (314)

  1. Ackers P. 1993. Flow formulae for straight two-stage channels. J. Hydr. Res. 31: 509-531.
  2. Arcement, G.J. and Schneider, V.R. 1989. Guide for selecting Manning's roughness coefficients for natural channels and floodplains. U.S. Geological Survey Water Supply Paper 2339.
  3. ASCE Task Force on Friction Factors 1963. Friction factors in open channels. J. Hydr. Div. ASCE 89: 97-143.
  4. Babaeyan-Koopaei, K., Ervine, D.A., Carling, P.A. and Cao, Z. 2002. Velocity and Turbulence Measurements for Two Overbank Flow Events in River Severn. J. Hydr. Engrg. 128(10): 891-900.
  5. Bakry, M.F., Gates, T.K. and Khattab, A.F. 1992. Field-measured hydraulic resistance characteristics in vegetation-infested canals. Journal of Irrigation and Drainage Engineering 118(2): 256-274.
  6. Barnes, H.H. 1967. Roughness characteristics of natural channels: color photographs and descriptive data for 50 stream channels for which roughness coefficients have been determined. US Geological Survey Water-Supply Paper 1849.
  7. Becker, K. 1999. Der Einfluß von kurzen Gehölzstreifen auf den Hochwasserabfluß in Flüssen mit gegliedertem Querschnitt. Mitteilungen 202. Institut für Wasserwirtschaft und Kulturtechnik, Universität Karlsruhe. [Doctoral thesis]
  8. Bertram, H.-U. 1985. Über den Abfluß in Trapezgerinnen mit extremer Böschungsrauheit. Mitteilungen 86. Leichtweiss-Institut für Wasserbau, Technische Universität Braunschweig. [Doctoral thesis]
  9. Bohn, B.A. and Kershner, J.L. 2002. Establishing aquatic restoration priorities using a watershed approach. Journal of Environmental Management 64(4): 355-363.
  10. Broadhurst, L.J., Heritage, G.L., van Niekerk, A.W., James, C.S. and Rogers, K.H. 1997. Translating discharge into local hydraulic conditions on the Sabie River: an assessment of channel flow resistance. Water Research Commission WRC Report 474/2/97.
  11. Brookes, A. and Sear, D. 1996. Geomorphological principles for restoring channels. In: Brookes, A. and Shields, F.D. (eds.). River channel restoration: guiding principles for sustainable projects. John Wiley, Chichester. p. 75- 101.
  12. Brookes, A. 1996. Floodplain restoration and rehabilitation. In: Anderson, M., Walling, D. and Bates, P. (eds.). Floodplain processes. John Wiley, Chichester. p. 553-576.
  13. BWK 1999. Hydraulische Berechnung von naturnahen Fließgewässern, Teil 1: Stationäre Berechnung der Wasserspiegellinie unter besonderer Berücksichtigung von Bewuchs-und Bauwerkseinflüssen. Merkblatt 1. Bund der Ingenieure für Wasserwirtschaft, Abfallwirtschaft und Kulturbau e.V., Düsseldorf. BWK 2000. Hydraulische Berechnung von naturnahen Fließgewässern, Teil 2: Grundlagen für stationäre, eindimensionale Wasserspiegellagen- berechnungen. Berichte 1. Bund der Ingenieure für Wasserwirtschaft, Abfallwirtschaft und Kulturbau e.V., Düsseldorf.
  14. Chow, V.T. 1959. Open-channel hydraulics. McGraw-Hill, New York.
  15. Coon, W.F. 1998. Estimation of roughness coefficients for natural stream channels with vegetated banks. US Geological Survey Water-Supply Paper 2441.
  16. Cowan, W.L. 1956. Estimating hydraulic roughness coefficients. Agricultural Engineering 37: 473-475.
  17. Darby, S.E. 1999. Effect of Riparian Vegetation on Flow Resistance and Flood Potential. J. Hydr. Engrg. 125: 443-454.
  18. Dittrich, A. 1998. Wechselwirkung Morphologie/Strömung naturnaher Fließgewässer. Mitteilungen 198. Institut für Wasserwirtschaft und Kulturtechnik, Universität Karlsruhe.
  19. DVWK 1991. Hydraulische Berechnung von Fließgewässern. Merkblätter 220. Deutscher Verband für Wasserwirtschaft und Kulturbau e.V., Bonn. DVWK 1996. Fluß und Landschaft -ökologische Entwicklungskonzepte. Merkblätter 240. Deutscher Verband für Wasserwirtschaft und Kulturbau e.V., Bonn.
  20. Dyson, M., Bergkamp, G. and Scanlon, J. (eds.) 2003. Flow: The Essentials of Environmental Flows. IUCN, Gland and Cambridge.
  21. Einstein, H.A. and Banks, R.B. 1950. Fluid resistance of composite roughness. Trans. AGU 31: 603-610.
  22. El-Hakim, O. and Salama, M.M. 1992. Velocity distribution inside and above branched flexible roughness. Journal of Irrigation and Drainage Engineering 118(6): 914-927.
  23. Escarameia, M., Gasowski, Y. and May, R. 2002. Grassed drainage channels hydraulic resistance characteristics. Water and Maritime Engineering 154(4): 333-341.
  24. Evers, P. 1983. Untersuchung der Strömungsvorgänge in gegliederten Gerinnen mit extremen Rauheitsunterschieden. Mitteilungen 45. Institut für Wasserbau und Wasserwirtschaft, Technische Hochschule Aachen. [Doctoral thesis]
  25. Fathi-Moghadam, M. 1996. Momentum absorption in non-rigid, non- submerged, tall vegetation along rivers. University of Waterloo. [Doctoral thesis] Fathi-Moghadam, M. and Kouwen, N. 1997. Nonrigid, nonsubmerged, vegetative roughness on floodplains. J. Hydr. Engrg. 123(1): 51-57.
  26. Fenzl, R.N. and Davis, J.R. 1964. Hydraulic resistance relationships for surface flows in vegetated channels. Trans. ASAE 7: 46-55.
  27. Fischenich, J.C. 1996. Velocity and Resistance in Densely Vegetated Floodways. Colorado State University. [Doctoral thesis]
  28. Fischer-Antze, T., Stoesser, T., Bates, P. and Olsen, N.R.B. 3D numerical modelling of open-channel flow with submerged vegetation. J. Hydr. Res. 39(3): 303-310.
  29. Fisher, K. 1995. The impact of temporal and spatial variations in vegetation in rivers. Report SR 393. HR Wallingford Ltd, Wallingford.
  30. Fisher, K. 2001. Handbook for assessment of hydraulic performance of environmental channels. Report SR 490. HR Wallingford Ltd, Wallingford.
  31. Flippin-Dudley, S.J., Abt, S.R., Bonham, C.D., Watson, C.C. and Fischenich, J.C. 1998. Evaluation of flow-resistance equations for vegetated channels and floodplains. Technical Report EL-98-2. U.S. Army Engineer Research and Development Center, Vicksburg, MS.
  32. Freeman, G.E., Rahmeyer, W.H. and Copeland, R.R. 2000. Determination of resistance due to shrubs and woody vegetation. Technical Report ERDC/CHL TR-00-25. U.S. Army Engineer Research and Development Center, Vicksburg, MS.
  33. Gerstgraser, C. 2000. Ingenieurbiologische Bauweisen an Fliessgewässern. Grundlagen zu Bau, Belastbarkeit und Wirkungsweisen. Dissertationen der Universität für Bodenkultur Wien 52. Österreichischer Kunst-und Kulturverlag, Wien. [Doctoral thesis]
  34. Haber, B. 1982. Über den Erosionsbeginn bei der Uberströmung von flexibelen Rauheitselementen. Mitteilungen 74. Leichtweiss-Institut für Wasserbau, Technische Universität Braunschweig. [Doctoral thesis]
  35. Helmiö, T. 2002. Unsteady 1D flow model of compound channel with vegetated floodplains. Journal of Hydrology 269(1-2): 89-99.
  36. Helmiö, T. and Järvelä, J. 1998. Assessing the hydraulic performance in river rehabilitation projects -Myllypuro Brook case study. In: Kajander, J. (ed.). NHP Report 44. XX Nordic Hydrological Conference, Helsinki. p. 357-364.
  37. Hicks, D.M. and Mason, P.D. 1999. Roughness Characteristics of New Zealand Rivers. NIWA, Christchurch.
  38. Horton, R.E. 1945. Erosional development of streams and their drainage basins; hydrophysical approach to quantitative morphology. Bulletin of the Geological Society of America 56: 275-370.
  39. Hosia, L. 1983. Pienten uomien virtausvastuskerroin: yleiskatsausosa [Resistance coefficient of small channels]. Helsinki. [In Finnish]
  40. Huang, H.Q. and Nanson, G.C. 1997. Vegetation and channel variation; a case study of four small streams in southeastern Australia. Geomorphology 18: 237-249.
  41. Hunzinger, L.M. 1998. Flussaufweitungen -Morphologie, Geschiebehaushalt und Grundsätze zur Bemessung. Mitteilungen 159. Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, ETH Zürich. [Doctoral thesis] Hydraulics Research 1988. Assessing the hydraulic performance of environmentally acceptable channels. Report EX 1799. Hydraulics Research Ltd., Wallingford.
  42. Ikeda, S. and Kanazawa, M. 1996. Three-dimensional organized vortices above flexible water plants. J. Hydr. Engrg. 122(11): 634-640.
  43. Indlekofer, H. 1981. Überlagerung von Rauhigkeitseinflüssen beim Abfluß in offenen Gerinnen. Mitteilungen 37. Institut für Wasserbau und Wasserwirtschaft, Technische Hochschule Aachen.
  44. Jacobs, J.M. and Wang, M.-H. 2003. Atmospheric Momentum Roughness Applied to Stage-Discharge Relationships in Flood Plains. Journal of Hydrologic Engineering 8(2): 99-104.
  45. James, C.S., Birkhead, A.L., Jordanova, A.A., Kotschy, K.A., Nicolson, C.R. and Makoa, M.J. 2001. Interaction of reeds, hydraulics and river morphology. Water Research Commission Report 856/1/01. Pretoria, South Africa.
  46. Järvelä, J. 1998. Luonnonmukainen vesirakennus: periaatteet ja hydrauliset näkökohdat virtavesien ennallistamisessa ja uudisrakentamisessa [Environmental river engineering and restoration: guiding principles and hydraulic performance]. Helsinki University of Technology Water Resources Publications 1. [In Finnish]
  47. Järvelä, J. and Helmiö, T. 1999. Hydraulic features of boreal river rehabilitation -Finnish experience. Proceedings of the 3rd International Symposium on Ecohydraulics. Utah State University, Salt Lake City.
  48. Jordanova, A.A. and James, C.S. 2003. Experimental study of bed load transport through emergent vegetation. J. Hydr. Engrg. 129(6): 474-478.
  49. Jordanova, A.A., Rowlston, W.S., Birkhead, A.L. and James, C.S. 1999. The role of hydraulics in holistic instream flow requirement assessment. Conference on integrated management of river ecosystems: an international experience. South Africa.
  50. Jungwirth, M., Muhar, S. and Schmutz, S. 2002. Re-establishing and assessing ecological integrity in riverine landscapes. Freshwater Biology 47: 867-887.
  51. Kadlec, R.H. 1990. Overland flow in wetlands: vegetation resistance. J. Hydr. Engrg. 116(5): 691-706.
  52. Kaiser, W. 1984. Fliesswiderstandsverhalten in Gerinnen mit durchströmten Ufergehölzen. Wasserbau-Mitteilungen 23. Institut für Wasserbau, konstruktiven Wasserbau und Wasserwirtschaft, Technische Hochschule Darmstadt. [Doctoral thesis]
  53. Kaitera, P. 1934. Järvenlasku-ja joenperkaushankkeiden suunnittelua varten suoritettavasta hydrometrisestä tutkimuksesta. Eripainos Teknillisestä Aikakauslehdestä N:osta 5-6. Helsingin Uusi Kirjapaino O.-Y., Helsinki. [In Finnish]
  54. Kao, T.Y. and Barfield, B.J. 1978. Predictions of Flow Hydraulics of Vegetated Channels. Trans. ASAE 21(3): 489-494.
  55. King, J.M., Tharme, R.E. and de Villiers, M.S. (eds.) 2000. Environmental flow assessments for rivers: manual for the Building Block Methodology. Water Research Commission Report TT 131/00. Pretoria, South Africa.
  56. Klaassen, G.J. and Zwaard, J.J. 1974. Roughness coefficients of vegetated floodplains. J. Hydr. Res. 12(1): 43-63.
  57. Knight, D.W. and Shiono, K. 1996. River channel and floodplain hydraulics. In: Anderson, M., Walling, D. and Bates, P. (eds.). Floodplain processes. John Wiley, Chichester. p. 139-182.
  58. Kouwen, N. 1988. Field estimation of the biomechanical properties of grass. J. Hydr. Res. 26(5): 559-568.
  59. Kouwen, N. and Fathi-Moghadam, M. 2000. Friction Factors for Coniferous Trees along Rivers. J. Hydr. Engrg. 126(10): 732-740.
  60. Kouwen, N. and Li, R.-M. 1980. Biomechanics of vegetative channel linings. J. Hydr. Div. ASCE 106(6): 1085-1103.
  61. Kouwen, N. and Unny, T.E. 1973. Flexible roughness in open channels. J. Hydr. Div. ASCE 99(5): 713-728.
  62. Kouwen, N., Li, R.M. and Simons, D.B. 1981. Flow Resistance in Vegetated Waterways. Trans. ASAE 24(3): 684-698.
  63. Kouwen, N., Unny, T.E. and Hill, H.M. 1969. Flow retardance in vegetated channels. Journal of Irrigation and Drainage Division 95(2): 329-340.
  64. Kutija, V. and Hong, T.M.H. 1996. A numerical model for assessing the additional resistance to flow introduced by flexible vegetation. J. Hydr. Res. 34(1): 99-114.
  65. Li, R.-M. and Shen, H.W. 1973. Effect of tall vegetations on flow and sediment. J. Hydr. Div. ASCE 99(5): 793-814.
  66. Lindner, K. 1982. Der Strömungswiderstand von Pflanzenbeständen. Mitteilungen 75. Leichtweiss-Institut für Wasserbau, Technische Universität Braunschweig. [Doctoral thesis]
  67. López, F. and García, M.H. 2001. Mean flow and turbulence structure of open- channel flow through non-emergent vegetation. J. Hydr. Engrg. 127(5): 392- 402. Maione, U., Monti, R. and Romiti, R. 2000. Hydraulic drag in vegetated channels -A campaign investigation. In: Maione, U., Lehto, M. and Monti, R. (eds.). Proceedings of an international conference New Trends in Water and Environmental Engineering for Safety and Life. Balkema, Rotterdam.
  68. Manga, M. and Kirchner, J.W. 2000. Stress partitioning in streams by large woody debris. Water Resources Research 36(8): 2373-2379.
  69. Masterman, R. and Thorne, C.R. 1992. Predicting influence of bank vegetation on channel capacity. J. Hydr. Engrg. 118(7): 1052-1058.
  70. McKenney, R., Jacobson, R.B. and Wertheimer, R.C. 1995. Woody vegetation and channel morphogenesis in low-gradient, gravel-bed streams in the Ozark Plateaus, Missouri and Arkansas. Geomorphology 13: 175-198.
  71. McMahon, T.A. 1975. The mechanical design of trees. Sci. Am. 233(1): 92- 102.
  72. McMahon, T.A. and Kronauer, R.E. 1976. Tree structures: deducing the principle of mechanical design. J. theor. Biol. 59: 443-466.
  73. Meijer, D.G. and van Velzen, E.H. 1999. Prototype-scale flume experiments on hydraulic roughness of submerged vegetation. Proceedings of the 28th IAHR Congress. Graz, Austria.
  74. Mertens, W. 1989. Zur Frage hydraulischer Berechnungen naturnaher Fließgewässer. Wasserwirtschaft 79(4): 170-179.
  75. Muhar, S. 1996. Habitat improvement of Austrian rivers with regard to different scales. Regulated Rivers: Research and Management 12(5): 471-482.
  76. Naot, D., Nezu, I. and Nakagawa, H. 1996. Unstable Patterns in Partly Vegetated Channels. J. Hydr. Engrg. 122(11): 671-673.
  77. Nash, J.E. and Sutcliffe, J.V. 1970. River flow forecasting through conceptual models, Part I -A discussion of principles. Journal of Hydrology 10(3): 282- 290. National Board of Waters 1984. Hydrologiset havainto-ja mittausmenetelmät [Hydrological observation and measurement methods]. Publication of the Water Administration 47. [In Finnish]
  78. Nepf, H.M. 1999. Drag, turbulence, and diffusion in flow through emergent vegetation. Water Resources Research 35(2): 479-489.
  79. Nepf, H.M. and Vivoni, E.R. 2000. Flow structure in depth-limited, vegetated flow. J. Geophys. Res. 105(C12): 28547-28557.
  80. Newson, M.D. 1992. River conservation and catchment management. In: Boon, P.J., Calow, P. and Petts, G.E. (eds.). River conservation and management. John Wiley, Chichester. p. 385-396.
  81. Nezu, I. and Nakagawa, H. 1993. Turbulence in open-channel flows. Balkema, Rotterdam.
  82. Nikora, V.I. and Goring, D.G. 1998. ADV measurements of turbulence: can we improve their interpretation? J. Hydr. Engrg. 124(6): 630-634.
  83. Nuding, A. 1991. Fließwiderstandsverhalten in Gerinnen mit Ufergebüsch. Wasserbau-Mitteilungen 35. Technische Hochschule Darmstadt. [Doctoral thesis]
  84. Oplatka, M. 1998. Stabilität von Weidenverbauungen an Flussufern. Mitteilungen 156. Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, ETH Zürich. [Doctoral thesis]
  85. Palmer, V.J. 1945. A method for designing vegetated waterways. Agric. Eng. 26(12): 516-520.
  86. Pasche, E. 1984. Turbulenzmechanismen in naturnahen Fließgewässern und die Möglichkeiten ihrer mathematischen Erfassung. Mitteilungen 52. Institut für Wasserbau und Wasserwirtschaft, Technische Hochschule Aachen. [Doctoral thesis]
  87. Pasche, E. and Rouvé, G. 1985. Overbank flow with vegetatively roughened flood plains. J. Hydr. Engrg. 111(9): 1262-1278.
  88. Petryk, S. and Bosmajian, G.B. 1975. Analysis of flow through vegetation. J. Hydr. Div. ASCE 101(7): 871-884.
  89. Plate, E.J. and Quraishi, A.A. 1965. Modeling of velocity distributions inside and above tall crops. Journal of Applied Meteorology 4: 400-408.
  90. Raupach, M.R., Thom, A.S. and Edwards, I. 1980. A wind-tunnel study of turbulent flow close to regularly arrayed rough surfaces. Boundary Layer Meteorology 18: 373-397.
  91. Rauws, G. 1988. Laboratory experiments of resistance to overland flow due to composite roughness. Journal of Hydrology 103: 37-52.
  92. Ree, W.O. 1949. Hydraulic characteristics of vegetation for vegetated waterways. Agric. Eng. 30(4): 184-189.
  93. Ree, W.O. and Crow, F.R. 1977. Friction factors for vegetated waterways of small slope. Agricultural Research Service ARS-S-151. U.S. Department of Agriculture, Washington, D.C.
  94. Rickert, K. 1986. Der Einfluß von Gehölzen auf die Lichtverhältnisse und das Abflußverhalten in Fließgewässern. Mitteilungen 61. Inst. für Wasserwirtschaft, Hydrologie und Landwirtschaftlichen Wasserbau, Universität Hannover. [Doctoral thesis]
  95. Rouse, H. 1965. Critical analysis of open-channel resistance. J. Hydr. Div. ASCE 91(4): 1-25.
  96. Rouse, H. and Ince, S. 1963. History of hydraulics. Dover Publications, New York.
  97. Rouvé, G. (ed.) 1987. Hydraulische Probleme beim naturnahen Gewässerausbau. Deutsche Forschungsgemeinschaft (DFG), Weinheim.
  98. Saari, S. 1955. Hankauskertoimen arvosta pienissä vesiväylissä [On the value of the rugosity coefficient in small channels]. Teknillinen korkeakoulu, Helsinki. [In Finnish]
  99. Samani, J.M.V. and Kouwen, N. 2002. Stability and Erosion in Grassed Channels. J. Hydr. Engrg. 128(1): 40-45.
  100. Schlichting, H. and Gersten, K. 2000. Boundary layer theory. 8th revised and enlarged edition. Springer, Berlin.
  101. Schumacher, F. 1995. Zur Durchflußberechnung gegliederter, naturnah gestallter Fließgewässer. Mitteilungen 127. Institut für Wasserbau und Wasserwirtschaft, Technische Universität Berlin. [Doctoral thesis]
  102. Schumm, S.A. 1956. Evolution of drainage systems and slopes in badlands at Perth Amboy, New Jersey. Bulletin of the Geological Society of America 67: 597-646. SCS 1954. Handbook of channel design for soil and water conservation. Soil Conservation Service SCS-TP-61. U.S. Department of Agriculture, Washington, D.C.
  103. Seifert, A. 1938. Naturnäherer Wasserbau. Deutsche Wasserwirtschaft 33(12): 361-366.
  104. Sellin, R.H.J. 1964. A laboratory investigation into the interaction between the flow in the channel of a river and that over its flood plain. La Houille Blanche 19(7): 793-802.
  105. Sellin, R.H.J. and van Beesten, D. 2002. Berm vegetation and its effects on flow resistance in a two-stage river channel: an analysis of field data. In: Bousmar, D. and Zech, Y. (eds.). River Flow 2002. p. 319-327.
  106. Shields, F.D. and Gippel, C.J. 1995. Prediction of effects of woody debris removal on flow resistance. J. Hydr. Engrg. 121(4): 341-354.
  107. Shields, F.D., Copeland, R.R., Klingeman, P.C., Doyle, M.W. and Simon, A. 2003. Design for stream restoration. J. Hydr. Engrg. 129(8): 575-584.
  108. Shimizu, Y. and Tsujimoto, T. 1994. Numerical Analysis of Turbulent Open- Channel Flow Over a Vegetation Layer Using a k-ε Turbulence Model. Journal of Hydroscience and Hydraulic Engineering 11(2): 57-67.
  109. Sokolov, Yu.N. 1980. Hydraulic resistance of floodplains. Water Resources 5: 563-572.
  110. Specht, F.-J. 2002. Einfluß von Gerinnebreite und Uferbewuchs auf die hydraulisch-sedimentologischen Verhältnisse naturnaher Fließgewässer. Fachbereich Bauingenieurwesen, Technische Universität Braunschweig. [Doctoral thesis]
  111. Stephan, U. 2002. Zum Fließwiderstandsverhalten flexibler Vegetation. Wiener Mitteilungen 180. Institut für Hydraulik, Gewässerkunde und Wasserwirtschaft, Technische Universität Wien. [Doctoral thesis]
  112. Stephan, U. and Gutknecht, D. 2002. Hydraulic resistance of submerged flexible vegetation. Journal of Hydrology 269(1-2): 27-43.
  113. Stone, B.M. and Shen, H.T. 2002. Hydraulic Resistance of Flow in Channels with Cylindrical Roughness. J. Hydr. Engrg. 128(5): 500-506.
  114. Strahler, A.N. 1952. Hypsometric (area-altitude) analysis of erosional topography. Bulletin of the Geological Society of America 63: 1117-1142.
  115. Temple, D.M. 1986. Velocity distribution coefficients for grass-lined channels. J. Hydr. Engrg. 112(3): 193-205.
  116. Temple, D.M. 1987. Closure to 'Velocity distribution coefficients for grass-lined channels'. J. Hydr. Engrg. 113(9): 1221-1226.
  117. Temple, D.M. 1991. Changes in Vegetal Flow Resistance During Long- Duration Flows. Trans. ASAE 34(4): 1769-1774.
  118. Temple, D.M. 1999. Flow resistance of grass-lined channel banks. Applied Engineering in Agriculture 15(2): 129-133.
  119. Temple, D.M., Robinson, K.M., Ahring, R.M. and Davis, A.G. 1987. Stability Design of Grass-Lined Open Channels. USDA Agriculture Handbook 667. U.S. Department of Agriculture, Washington, D.C.
  120. Thompson, G.T. and Roberson, J.A. 1976. A theory of flow resistance for vegetated channels. Trans. ASAE 19(2): 288-293.
  121. Thornton, C.I., Abt, S.R., Morris, C.E. and Fischenich, J.C. 2000. Calculating shear stress at channel-overbank interfaces in straight channels with vegetated floodplains. J. Hydr. Engrg. 126(12): 929-936.
  122. Tsihrintzis, V.A. 2001. Variation of roughness coefficients for unsubmerged and submerged vegetation. J. Hydr. Engrg. 127(3): 239-245.
  123. Tsujimoto, T. 1999. Fluvial processes in streams with vegetation. J. Hydr. Res. 37(6): 789-803.
  124. Tsujimoto, T., Kitamura, T. and Okada, T. 1992. Turbulent open-channel flow over bed covered by rigid vegetation. Journal of Hydroscience and Hydraulic Engineering 10(2): 13-25.
  125. Tsujimoto, T., Kitamura, T., Fujii, Y. and Nakagawa, H. 1996. Hydraulic resistance of flow with flexible vegetation in open channel. Journal of Hydroscience and Hydraulic Engineering 14(1): 47-56.
  126. Vogel, S. 1994. Life in moving fluids: the physical biology of flow. 2nd edition. Princeton University Press, Princeton.
  127. Wahl, T. 2000. Analyzing ADV Data Using WinADV. ASCE Joint Conference on Water Resources Engineering and Water Resources Planning and Management. Minneapolis, USA.
  128. Watanabe, T. and Kondo, J. 1990. The influence of canopy structure and density upon the mixing length within and above vegetation. Journal of Meteorological Society of Japan 68(2): 227-234.
  129. Werth, D. 1997. Predicting Resistance and Stability of Vegetation in Floodplains. Utah State University. [Doctoral thesis]
  130. Wessels, W.P.J. and Strelkoff, T. 1968. Established surge on an impervious vegetated bed. Journal of Irrigation and Drainage Division 94(1): 1-23.
  131. Wilson, C.A.M.E., Stoesser, T., Bates, P.D. and Batemann Pinzen, A. 2003. Open Channel Flow through Different Forms of Submerged Flexible Vegetation. J. Hydr. Engrg. 129(11): 847-853.
  132. Wu, F.-C., Shen, H.W. and Chou, Y.-J. 1999. Variation of Roughness Coefficients for Unsubmerged and Submerged Vegetation. J. Hydr. Engrg. 125(9): 934-942.
  133. Yen, B.C. 2002. Open Channel Flow Resistance. J. Hydr. Engrg. 128(1): 20-39. References
  134. Chen, C.I., 1976. Flow resistance in broad shallow grassed channels. Journal of the Hydraulics Division, ASCE 102 (3), 307 -322.
  135. Chow, V.T., 1959. Open-Channel Hydraulics, McGraw-Hill Book Co, p. 680.
  136. Fathi-Maghadam, M., Kouwen, N., 1997. Nonrigid, nonsubmerged, vegetative roughness on floodplains. Journal of Hydraulic Engineering 123 (1), 51-57.
  137. Kouwen, N., 1988. Field estimation of the biomechanical properties of grass. Journal of Hydraulic Research 26 (5), 559-568.
  138. Kouwen, N., Fathi-Moghadam, M., 2000. Friction factors for coniferous trees along rivers. Journal of Hydraulic Engineering 126 (10), 732-740.
  139. Kouwen, N., Li, R.-M., 1980. Biomechanics of vegetative channel linings. Journal of the Hydraulics Division, ASCE 106 (6), 1085-1103.
  140. Kouwen, N., Unny, T.E., 1973. Flexible roughness in open channels. Journal of the Hydraulics Division, ASCE 99 (5), 713 -728.
  141. Li, R.-M., Shen, H.W., 1973. Effect of tall vegetations on flow and sediment. Journal of the Hydraulics Division, ASCE 99 (5), 793 -814.
  142. Oplatka, M., 1998. Stabilita ¨t von Weidenverbauungen an Flussu- fern, Mitteilungen der Versuchsanstalt fu ¨r Wasserbau, Hydro- logie und Glaziologie, No. 156, ETH Zu ¨rich, p. 217.
  143. Pasche, E., 1984. Turbulenzmechanismen in naturnahen Fließgewa ¨ssern und die Mo ¨glichkeiten ihrer mathematischen Erfassung, Mitteilungen Institut fu ¨r Wasserbau und Wasser- wirtschaft, No. 52, RWTH Aachen, p. 243.
  144. Pasche, E., Rouve ´, G., 1985. Overbank flow with vegetatively roughened flood plains. Journal of Hydraulic Engineering 111 (9), 1262-1278.
  145. Petryk, S., Bosmajian, G.B., 1975. Analysis of flow through vegetation. Journal of the Hydraulics Division, ASCE 101 (7), 871 -884.
  146. Rouve ´, G. (Ed.), 1987. Hydraulische Probleme beim naturnahen Gewa ¨sserausbau. Deutsche Forschungsgemeinschaft (DFG), Weinheim, p. 267.
  147. Stephan, U., 2001. Zum Fliesswiderstandsverhalten flexibler Vegetation. Technische Universita ¨t Wien, PhD thesis, Fukulta ¨t fu ¨r Bauingenieurwesen, p. 165.
  148. Tsujimoto, T., Kitamura, T., Fujii, Y., Nakagawa, H., 1996. Hydraulic resistance of flow with flexible vegetation in open channel. Journal of Hydroscience and Hydraulic Engineering 14 (1), 47-56.
  149. Wu, F.-C., Shen, H.W., Chou, Y-J., 1999. Variation of roughness coefficients for unsubmerged and submerged vegetation. Journal of Hydraulic Engineering 125 (9), 934-942.
  150. Brookes, A. & Shields, F.D. (eds) 1996. River channel restora- tion: guiding principles for sustainable projects. Chiches- ter: John Wiley.
  151. Fischenich, C. & Dudley, S. 2000. Determining drag coeffi- cients and area for vegetation. EMRRP Technical Notes Collection, TN EMRRP-SR-8. U.S. Army Engineer Re- search and Development Center, Vicksburg, MS.
  152. Freeman, G.E., Rahmeyer, W.H., & Copeland, R.R. 2000. De- termination of resistance due to shrubs and woody vegeta- tion. Technical Report, ERDC/CHL TR-00-25. U.S. Army Engineer Research and Development Center, Vicksburg, MS. Järvelä, J. (in press). Flow resistance of flexible and stiff vege- tation: a flume study with natural plants.
  153. Kadlec, R.H. 1990. Overland flow in wetlands: vegetation re- sistance. Journal of Hydraulic Engineering, 116(5): 691- 706.
  154. Klaassen, G.J. & Zwaard, J.J. 1974. Roughness coefficients of vegetated floodplains. Journal of Hydraulic Research, 12(1): 43-63.
  155. Kouwen, N. & Unny, T.E. 1973. Flexible roughness in open channels. Journal of the Hydraulics Division, ASCE, 99(5): 713-728.
  156. Kouwen, N. & Fathi-Moghadam, M. 2000. Friction Factors for Coniferous Trees along Rivers. Journal of Hydraulic Engi- neering, 126(10): 732-740.
  157. Li, R.-M. & Shen, H.W. 1973. Effect of tall vegetations on flow and sediment. Journal of the Hydraulics Division, ASCE, 99(5): 793-814.
  158. Lindner, K. 1982. Der Strömungswiderstand von Pflanzen- beständen. Mitteilungen Leichtweiss-Institut für Wasser- bau, No. 75. TU Braunschweig.
  159. Mertens, W. 1989. Zur Frage hydraulischer Berechnungen nat- urnaher Fließgewässer. Wasserwirtschaft, 79(4): 170-179.
  160. Nuding, A. 1991. Fliesswiderstandsverhalten in Gerinnen mit Ufergebüsch. Wasserbau-Mitteilungen, No. 35. TH Darm- stadt.
  161. Oplatka, M. 1998. Stabilität von Weidenverbauungen an Fluss- ufern. Mitteilungen der Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, No. 156. ETH Zürich.
  162. Pasche, E. 1984. Turbulenzmechanismen in naturnahen Fließgewässern und die Möglichkeiten ihrer mathema- tischen Erfassung. Mitteilungen Institut für Wasserbau und Wasserwirtschaft, No. 52. RWTH Aachen.
  163. Pasche, E. & Rouvé, G. 1985. Overbank flow with vegetatively roughened flood plains. Journal of Hydraulic Engineering, 111(9): 1262-1278.
  164. Petryk, S. & Bosmajian, G.B. 1975. Analysis of flow through vegetation. Journal of the Hydraulics Division, ASCE, 101(7): 871-884.
  165. Rouvé, G. (ed.) 1987. Hydraulische Probleme beim naturna- hen Gewässerausbau. Weinheim: Deutsche Forschungsge- meinschaft (DFG).
  166. Vogel, S. 1994. Life in moving fluids: the physical biology of flow. 2nd edition. Princeton: Princeton University Press.
  167. Wu, F.-C., Shen, H.W. & Chou, Y.-J. 1999. Variation of roughness coefficients for unsubmerged and submerged vegetation. Journal of Hydraulic Engineering, 125(9): 934- 942. REFERENCES
  168. Babaeyan-Koopaei, K., Ervine, D.A., Carling, P.A. and Cao Z. 2002. Velocity and Turbulence Measurements for Two Overbank Flow Events in River Severn. Journal of Hydraulic Engineering 128(10): 891-900.
  169. Carollo, F.G., Ferro, V. and Termini, D. Flow Velocity Measurements in Vegetated Channels. Journal of Hydraulic Engineering 128(7): 664-673.
  170. Freeman, G.E., Rahmeyer, W.H. and Copeland, R.R. 2000. Determination of resistance due to shrubs and woody vegetation. Technical Report, ERDC/CHL TR-00-25. U.S. Army Engineer Research and Development Center, Vicksburg, MS.
  171. Ikeda, S. and Kanazawa, M. 1996. Three-dimensional organized vortices above flexible water plants. Journal of Hydraulic Engineering 122(11): 634-640.
  172. Järvelä, J. 2002. Flow resistance of flexible and stiff vegetation: a flume study with natural plants. Journal of Hydrology 269(1-2): 44-54.
  173. Kouwen, N. and Fathi-Moghadam, M. 2000. Friction Factors for Coniferous Trees along Rivers. Journal of Hydraulic Engineering 126(10): 732-740.
  174. Kouwen, N. and Unny, T.E. 1973. Flexible roughness in open channels. Journal of the Hydraulics Division 99(5): 713-728.
  175. López, F. and García, M.H. 2001. Mean flow and turbulence structure of open-channel flow through non-emergent vegetation. Journal of Hydraulic Engineering 127(5): 392-402.
  176. Naot, D., Nezu, I. and Nakagawa, H. 1996. Unstable Patterns in Partly Vegetated Channels. Journal of Hydraulic Engineering 122(11): 671-673.
  177. Nepf, H.M. 1999. Drag, turbulence, and diffusion in flow through emergent vegetation. Water Resources Research 35(2): 479-489.
  178. Nepf, H.M. and Vivoni, E. R. 2000. Flow structure in depth-limited, vegetated flow. J. Geophys. Res. 105(C12): 28547-28557.
  179. Newson, M.D. 1992. River conservation and catchment management. In: Boon, P.J., Calow, P. and Petts, G.E. (eds.). River conservation and management. John Wiley, Chichester. pp. 385-396.
  180. Nikora, V. I. and Goring, D. G. 1998. ADV measurements of turbulence: can we improve their interpretation? Journal of Hydraulic Engineering 124(6): 630-634.
  181. Nikora, V., Goring, D., McEwan, I. and Griffiths, G. 2001. Spatially averaged open-channel flow over rough bed. Journal of Hydraulic Engineering 127(2): 123-133.
  182. Pasche, E. and Rouvé, G. 1985. Overbank flow with vegetatively roughened flood plains. Journal of Hydraulic Engineering 111(9): 1262-1278.
  183. Petryk, S. and Bosmajian, G.B. 1975. Analysis of flow through vegetation. Journal of the Hydraulics Division, ASCE, 101(7): 871-884.
  184. Shimizu, Y., and Tsujimoto, T. 1994. Numerical Analysis of Turbulent Open-Channel Flow Over a Vegetation Layer Using a k-ε Turbulence Model. Journal of Hydroscience and Hydraulic Engineering 11(2): 57-67.
  185. Stephan, U. 2001. Zum Fließwiderstandsverhalten flexibler Vegetation. Institute of Hydraulics, Hydrology and Water Resources Management, Faculty of Civil Engineering, Technical University of Vienna. PhD Thesis. 165 pp.
  186. Stephan, U. and Gutknecht, D. 2002. Hydraulic resistance of submerged flexible vegetation. Journal of Hydrology 269(1-2): 27-43.
  187. Stone, B.M. and Shen, H.T. 2002. Hydraulic Resistance of Flow in Channels with Cylindrical Roughness. Journal of Hydraulic Engineering 128(5): 500-506.
  188. Tsujimoto, T. 1999. Fluvial processes in streams with vegetation. Journal of Hydraulic Research 37(6): 789-803.
  189. Tsujimoto, T., Kitamura, T. and Okada, T. 1992. Turbulent open-channel flow over bed covered by rigid vegetation. J. of Hydroscience and Hydraulic Engineering 10(2): 13-25.
  190. Wahl, T. 2000. Analyzing ADV Data Using WinADV. ASCE Joint Conference on Water Resources Engineering and Water Resources Planning & Management, Minneapolis July 30 -August 2, 2000, USA. 10 pp.
  191. Ward, J.V., Tockner, K., Uehlinger, U. and Malard, F. 2001. Understanding natural patterns and processes in river corridors as the basis for effective river restoration. Regulated Rivers: Research & Management 17: 311-323.
  192. Barnes, H.H. (1967). Roughness characteristics of natu- ral channels: color photographs and descriptive data for 50 stream channels for which roughness coefficients have been determined. US Geological Survey Water-Supply Paper 1849.
  193. Chow, V.T. (1959). Open-channel hydraulics. McGraw-Hill, New York.
  194. Coon, W.F. (1998). Estimation of roughness coefficients for natural stream channels with vegetated banks. US Geological Survey Water-Supply Paper 2441.
  195. DVWK (1991). Hydraulische Berechnung von Fließgewässern. Merkblätter 220, Deutscher Verband für Wasserwirtschaft und Kulturbau e.V.
  196. Einstein, H.A. and Banks, R.B. (1950). "Fluid resistance of composite roughness", Trans. AGU, 31, 603-610.
  197. Fathi-Moghadam, M. (1996). Momentum absorption in non-rigid, non-submerged, tall vegetation along rivers. University of Waterloo, Canada. (Doctoral thesis.)
  198. Fathi-Moghadam, M. and Kouwen, N. (1997). "Non- rigid, nonsubmerged, vegetative roughness on floodplains", J. Hydr. Engrg., 123(1), 51-57.
  199. Freeman, G.E., Rahmeyer, W.H. and Copeland, R.R. (2000). Determination of resistance due to shrubs and woody vegetation. Technical Report, ERDC/CHL TR-00-25, U.S. Army Engineer Research and Development Center, Vicksburg, MS.
  200. Hicks, D.M. and Mason, P.D. (1999). Roughness Charac- teristics of New Zealand Rivers. NIWA, Christchurch.
  201. Horton, R.E. (1945). "Erosional development of streams and their drainage basins: hydrophysical approach to quan- titative morphology", Bull. Geolog. Soc. Amer., 56, 275-370.
  202. Järvelä, J. (2002a). "Flow resistance of flexible and stiff vegetation: a flume study with natural plants", J. Hydrol., 269(1-2), 44-54.
  203. Järvelä, J. (2002b). Determination of flow resistance of vegetated channel banks and floodplains. In River Flow 2002 (Eds. Bousmar, D. and Zech, Y.), Swets & Zeitlinger, Lisse, pp. 311-318.
  204. Jordanova, A. and James, C.S. (2003). "Experimental study of bed load transport through emergent vegetation", J. Hydr. Engrg., 129(6), 474-478.
  205. Klaassen, G.J. and Zwaard, J.J. (1974). "Roughness coefficients of vegetated floodplains", J. Hydr. Res., 12(1), 43-63.
  206. Kouwen, N. (1992). "Modern approach to design of grassed channels", J. Irrig. Drainage Engng., 118(5), 733-743.
  207. Kouwen, N. and Fathi-Moghadam, M. (2000). "Friction Factors for Coniferous Trees along Rivers", J. Hydr. Engrg., 126(10), 732-740.
  208. Kouwen, N. and Li, R.-M. (1980). "Biomechanics of vegetative channel linings", J. Hydr. Div. ASCE, 106(6), 1085-1103.
  209. Kouwen, N. and Unny, T.E. (1973). "Flexible rough- ness in open channels", J. Hydr. Div. ASCE, 99(5), 713-728.
  210. Kutija, V. and Hong, T.M.H. (1996). "A numerical model for assessing the additional resistance to flow introduced by flexible vegetation", J. Hydr. Res., 34(1), 99-114.
  211. Li, R.-M. and Shen, H.W. (1973). "Effect of tall vegeta- tions on flow and sediment", J. Hydr. Div. ASCE, 99(5), 793-814.
  212. Lindner, K. (1982). Der Strömungswiderstand von Pflanzenbeständen. Mitteilungen 75, Leichtweiss-Institut für Wasserbau, TU Braunschweig. (Doctoral thesis.)
  213. López, F. and García, M.H. (2001). "Mean flow and turbu- lence structure of open-channel flow through non-emergent vegetation", J. Hydr. Engrg., 127(5), 392-402.
  214. McMahon, T.A. (1975). "The mechanical design of trees", Sci. Am., 233(1), 92-102.
  215. McMahon, T.A. and Kronauer, R.E. (1976). "Tree struc- tures: deducing the principle of mechanical design", J. Theor. Biol., 59, 443-466.
  216. Mertens, W. (1989). "Zur Frage hydraulischer Berechnun- gen naturnaher Fließgewässer", Wasserwirtschaft, 79(4), 170-179.
  217. Naot, D., Nezu, I. and Nakagawa, H. (1996). "Unsta- ble patterns in partly vegetated channels", J. Hydr. Engrg., 122(11), 671-673.
  218. Nash, J.E. and Sutcliffe, J.V. (1970). "River flow fore- casting through conceptual models, Part I -A discussion of principles", J. Hydrol., 10(3), 282-290.
  219. Nepf, H.M. (1999). "Drag, turbulence, and diffusion in flow through emergent vegetation", Water Resources Res., 35(2), 479-489.
  220. Nuding, A. (1991). Fliesswiderstandsverhalten in Gerin- nen mit Ufergebüsch, Wasserbau-Mitteilungen 35, TH Darmstadt. (Doctoral thesis.)
  221. Oplatka, M. (1998). Stabilität von Weidenverbauun- gen an Flussufern. Mitteilungen 156, Versuchsanstalt für Wasserbau, Hydrologie und Glaziologie, ETH Zürich. (Doctoral thesis.)
  222. Pasche, E. and Rouvé, G. (1985). "Overbank flow with vegetatively roughened flood plains", J. Hydr. Engrg., 111(9), 1262-1278.
  223. Petryk, S. and Bosmajian, G.B. (1975). "Analysis of flow through vegetation", J. Hydr. Div. ASCE, 101(7), 871-884.
  224. Rautiainen, M., Stenberg, P., Nilson, T., Kuusk, A. and Smolander, H. (2003). "Application of a forest reflectance model in estimating leaf area index of Scots pine stands using Landsat-7 ETM reflectance data", Can. J. Remote Sensing, 29(3), 314-323.
  225. Schumm, S.A. (1956). "Evolution of drainage systems and slopes in badlands at Perth Amboy, New Jersey", Bull. Geolog. Soc. Amer., 67, 597-646.
  226. SCS (1954). Handbook of channel design for soil and water conservation. Publication SCS-TP-61, Soil Conservation Service, U.S. Department of Agriculture, Washington, D.C.
  227. Shimizu, Y. and Tsujimoto, T. (1994). "Numerical analysis of turbulent open-channel flow over a vegetation layer using a k-ε turbulence model", J. Hydrosci. Hydraul. Engng., 11(2), 57-67.
  228. Smolander, H. and Stenberg, P. (1996). "Response of LAI-2000 estimates to changes in plant surfarce area index in a Scots pine stand", Tree Physiol., 16, 345-349.
  229. Stenberg, P., Nilson, T., Smolander, H. and Voipio, P. (2003). "Gap fraction based estimation of LAI in Scots pine stands subjected to experimental removal of branches and stems", Can. J. Remote Sensing, 29(3), 363-370.
  230. Stoesser, T., Wilson, C.A.M.E., Bates, P.D. and Dittrich, A. (2003). "Application of a 3D numerical model to a river with vegetated floodplains", J. Hydroinformat., 5(2), 99-112.
  231. Strahler, A.N. (1952). "Hypsometric (area-altitude) anal- ysis of erosional topography", Bull. Geolog. Soc. Amer., 63, 1117-1142.
  232. Szoszkiewicz, K., Kaluża, T., Leśny, J. and Chojnicki, B.H. (2003). Remote sensing analysis of the floodplain veg- etation structure within a section of the Middle Vistula River. Towards natural flood reduction strategies, Proceedings of the EcoFlood conference, Warsaw, 6-13 September 2003.
  233. Temple, D.M., Robinson, K.M., Ahring, R.M. and Davis, A.G. (1987). Stability Design of Grass-Lined Open Channels. Agriculture Handbook 667, U.S. Department of Agriculture, Washington, D.C.
  234. Thompson, G.T. and Roberson, J.A. (1976). "A theory of flow resistance for vegetated channels", Trans. ASAE, 19(2), 288-293.
  235. Tsujimoto, T., Kitamura, T., Fujii, Y. and Nakagawa, H. (1996). "Hydraulic resistance of flow with flexible vegeta- tion in open channel", J. Hydrosci. Hydraul. Engng., 14(1), 47-56.
  236. Vogel, S. (1994). Life in moving fluids: the physical biology of flow. 2nd edition, Princeton University Press, Princeton.
  237. Welles, J. (1990). "Some indirect methods of estimating canopy structure", Remote Sensing Reviews, 5(1), 31-43.
  238. Welles, J. and Cohen, S. (1996). "Canopy structure measurement by gap fraction analysis using commercial instrumentation", J. Experimental Botany, 47(302), 1335- 1342.
  239. Werth, D. (1997). Predicting Resistance and Stability of Vegetation in Floodplains. Utah State University, US. (Doctoral thesis.)
  240. Wu, F.-C., Shen, H.W. and Chou, Y.-J. (1999). "Variation of Roughness Coefficients for Unsubmerged and Submerged Vegetation", J. Hydr. Engrg., 125(9), 934-942.
  241. Yen, B.C. (2002). "Open Channel Flow Resistance", J. Hydr. Engrg., 128(1), 20-39.
  242. References ASCE Task Force on Friction Factors (1963) Friction factors in open channels. Journal of the hydraulics division 89, 97-143.
  243. Bakry, M.F., Gates, T.K. and Khattab A.F. (1992) Field-measured hydraulic resistance characteristics in vegetation-infested canals. Journal of Irrigation and Drainage Engineering 118(2), 256-274.
  244. Barnes, H.H. (1967) Roughness characteristics of natural channels: color photographs and descriptive data for 50 stream channels for which roughness coefficients have been determined. US Geological Survey Water-Supply Paper 1849.
  245. Broadhurst, L.J., Heritage, G.L., van Niekerk, A.W., James, C.S. and Rogers, K.H. (1997) Translating discharge into local hydraulic conditions on the Sabie River: an assessment of channel flow resistance. Water Research Commission WRC Report 474/2/97.
  246. Brookes, A. (1996) Floodplain restoration and rehabilitation. In: Anderson, M., Walling, D. and Bates P. (eds.), Floodplain processes. John Wiley, Chichester. pp. 553-576.
  247. Chow, V.T. (1959) Open-channel hydraulics. McGraw-Hill, New York.
  248. Coon, W.F. (1998) Estimation of roughness coefficients for natural stream channels with vegetated banks. US Geological Survey Water-Supply Paper 2441.
  249. DVWK (1996) Fluß und Landschaft -ökologische Entwicklungskonzepte. Merkblätter 240. Deutscher Verband für Wasserwirtschaft und Kulturbau e.V., Bonn. [In German]
  250. Einstein, H.A. and Banks, R.B. (1950) Fluid resistance of composite roughness. Transactions, AGU 31, 603-610.
  251. Fisher, K.R. (1995) The impact of temporal and spatial variations in vegetation in rivers. Report SR 393. HR Wallingford Ltd, Wallingford.
  252. Fisher, K. (2001) Handbook for assessment of hydraulic performance of environmental channels. Report SR 490. HR Wallingford Ltd, Wallingford. [CD-ROM]
  253. Helmiö, T. (1997) Determination of the resistance coefficients in open-channel flow -development of a computer program and its application, Master's thesis. Helsinki University of Technology, Department of Civil and Env. Engineering. [in Finnish]
  254. Hicks, D.M. and Mason, P.D. (1999) Roughness Characteristics of New Zealand Rivers. NIWA, Christchurch.
  255. Hosia, L. (1980) Pienten uomien virtausvastuskerroin [Resistance coefficient of small channels].
  256. Vesihallituksen tiedotus 199. Vesihallitus, Helsinki. [In Finnish]
  257. Huang, H.Q. and Nanson, G.C. (1997) Vegetation and channel variation; a case study of four small streams in southeastern Australia. Geomorphology 18, 237-249
  258. Jordanova, A.A., Rowlston, W.S., Birkhead, A.L. and James, C.S. (1999) The role of hydraulics in holistic instream flow requirement assessment. Conference on integrated management of river ecosystems: an international experience, South Africa.
  259. Järvelä, J. (2002) Flow resistance of flexible and stiff vegetation: a flume study with natural plants. Journal of Hydrology 269(1-2), 44-54.
  260. Järvelä, J. and Helmiö, T. (1999) Hydraulic features of boreal river rehabilitation -Finnish experience. Proceedings of the 3rd International Symposium on Ecohydraulics. Utah State University, Salt Lake City. [CD-ROM]
  261. Kouwen, N. and Fathi-Moghadam, M. (2000) Friction Factors for Coniferous Trees along Rivers. Journal of Hydraulic Engineering 126(10), 732-740.
  262. Kouwen, N. and Unny, T.E. (1973) Flexible Roughness in Open Channels. Journal of Hydraulics Division 99(5), 713-728.
  263. Lawless, M. and Robert, A. (2001) Scales of boundary resistance in coarse-grained channels: turbulent velocity profiles and implications. Geomorphology 39, 221-238.
  264. Lopez, F. and Garcia, M. (1997) Open-Channel Flow through Simulated Vegetation: Turbulence Modeling and Sediment Transport. USGS Wetlands Research Program Technical Report WRP-CP- 10.
  265. Maione, U., Monti, R. and Romiti, R. (2000) Hydraulic drag in vegetated channels -A campaign investigation. In: Maione U., Lehto M. and Monti R. (eds.). Proceedings of an international conference New Trends in Water and Environmental Engineering for Safety and Life. Balkema, Rotterdam. [CD-ROM]
  266. Manga, M. and Kirchner, J.W. (2000) Stress partitioning in streams by large woody debris. Water Resources Research 36 (8), 2373-2379.
  267. Masterman, R. and Thorne, C.R. (1992) Predicting influence of bank vegetation on channel capacity. Journal of Hydraulic Engineering 118(7), 1052-1058.
  268. McKenney, R., Jacobson, R.B. and Wertheimer, R.C. (1995) Woody vegetation and channel morphogenesis in low-gradient, gravel-bed streams in the Ozark Plateaus, Missouri and Arkansas. Geomorphology 13, 175-198
  269. Millar, R.G. (1999) Grain and form resistance in gravel-bed rivers, Journal of Hydraulic Research 37(3), 303-312.
  270. Muhar, S. (1996) Habitat improvement of Austrian rivers with regard to different scales. Regulated Rivers: Research & Management 12(5), 471-482.
  271. National Board of Waters (1984) Hydrologiset havainto-ja mittausmenetelmät [Hydrological observation and measurement methods]. Publication 47 of the Water Administration. [In Finnish]
  272. Nepf, H.M. (1999) Drag, turbulence and diffusion in flow through emergent vegetation. Water Resources Research 35(2), 479-489.
  273. Newson, M.D. (1992) River conservation and catchment management. In: Boon, P.J., Calow, P. and Petts, G.E. (eds.), River conservation and management. John Wiley, Chichester. pp. 385-396.
  274. Pasche, E. and Rouvé, G. (1985) Overbank Flow with Vegetatively Roughened Flood Plains. Journal of Hydraulic Engineering 111(9), 1262-1278.
  275. Petryk, S. and Bosmaijan, G. (1975) Analysis of Flow Through Vegetation. Journal of Hydraulics Division, ASCE 111(7), 871-884.
  276. Rouvé, G. (ed.) (1987) Hydraulische Probleme beim naturnahen Gewässerausbau. Deutsche Forschungsgemeinschaft (DFG), Weinheim.
  277. Sellin, R.H.J. and van Beesten, D. (2002) Berm vegetation and its effects on flow resistance in a two- stage river channel: an analysis of field data. In: Bousmar, D., Zech, Y. (eds.) River Flow 2002. pp. 319-327.
  278. Shields, F.D. and Gippel, C.J. (1995) Prediction of effects of woody debris removal on flow resistance. Journal of Hydraulic Engineering 121(4), 341-354.
  279. Shimizu, Y. and Tsujimoto, T. (1994) Numerical Analysis of Turbulent Open-Channel Flow Over a Vegetation Layer Using a k-e Turbulence Model. Journal of Hydroscience and Hydraulic Engineering 11(2), 57-67.
  280. Ward, J.V., Tockner, K., Uehlinger, U. and Malard, F. (2001) Understanding natural patterns and processes in river corridors as the basis for effective river restoration. Regulated Rivers: Research & Management 17, 311-323.
  281. Yen, B.C.Y. (2002) Open channel flow resistance. Journal of Hydraulic Engineering 128(1), 20-39. References
  282. Ackers P. 1993. Flow formulae for straight two-stage chan- nels. J. Hydraul. Res. 31: 509-531.
  283. ASCE Task Force on Friction Factors 1963. Friction factors in open channels. J. Hydraul. Div. ASCE 89: 97-143.
  284. Barnes H.H. 1967. Roughness characteristics of natural channels: color photographs and descriptive data for 50 stream channels for which roughness coefficients have been determined. US Geological Survey Water-Supply Paper 1849.
  285. Begemann W. & Schiechtl H.M. 1994. Ingenieurbiologie: Handbuch zum ökologischen Wasser-und Erdbau, Bau- verlag GmbH, Wiesbaden und Berlin.
  286. Bettess R. 1999. Flow resistance equations for gravel bed rivers. Proc. 28th IAHR Congress, Graz, Austria, August 1999 (CD-ROM).
  287. Brookes A. & Shields F.D. (eds.) 1996. River channel resto- ration: guiding principles for sustainable projects, John Wiley, Chichester.
  288. Chow V.T. 1959. Open-channel hydraulics. McGraw-Hill Book Co., Singapore.
  289. Coon W.F. 1998. Estimation of roughness coefficients for natural stream channels with vegetated banks. US Geo- logical Survey Water-Supply Paper 2441.
  290. Cowan W.L. 1956. Estimating hydraulic roughness coeffi- cients. Agricultural Engineering 37: 473-475.
  291. Darby S.E. 1999. Effect of riparian vegetation on flow resist- ance and flood potential. J. Hydraul. Eng. 125: 443-454.
  292. Darby S. & Thorne C. 1994. Fluvial maintenance operations in managed alluvial rivers. Aq. Conserv: Marine and Freshwater Ecos. 4: 365-379.
  293. Darby S. & Thorne C. 1996. Predicting stage-discharge curves in channels with bank vegetation. J. Hydraul. Eng. 122: 583-586.
  294. Duncan M. & Smart G. 1999. Flow resistance. An overview of formulae for alluvial channel flow estimation. Proc. New Zealand Hydrological Conference, Napier, 1999.
  295. Einstein H.A. & Banks R.B. 1950. Fluid resistance of com- posite roughness. Transactions, AGU. 31: 603-610.
  296. Fisher K.R. 1996. Handbook for assessment of hydraulic performance of environmental channels. Report SR 490 (draft). HR Wallingford, Great Britain. FISRWG 1998. Stream corridor restoration: principles, proc- esses, and practices. The Federal Interagency Stream Restoration Working Group (FISRWG). GPO Item No. 0120-A; SuDocs No. A 57.6/2:EN 3/PT.653.
  297. Garbrecht J. & Brown G.O. 1991. Calculation of total conveyance in natural channels. J. Hydraul. Eng. 117: 788-798.
  298. Graf W.H. 1998. Fluvial hydraulics. Flow and transport processes in channels of simple geometry, John Wiley & Sons. Helmiö T. 1997. Avouoman vastuskertoimien määritys -laskentaohjelman kehitys ja soveltaminen, Master's thesis, Helsinki University of Technology, Department of Civil and Env. Engineering.
  299. Hydraulics Research. 1988. Assessing the hydraulic perform- ance of environmentally acceptable channels, Report EX 1799. Wallingford, Great Britain.
  300. Indlekofer H. 1981. Überlagerung von Rauhigkeitseinflüssen beim Abfluß in offenen Gerinnen. Institut für Wasser- bau und Wasserwirtschaft, Rheinisch-Westfälische Tech- nische Hochschule Aachen. Mitteilungen 37: 105-145.
  301. James C.S. 1994. Evaluation of methods for predicting bend loss in meandering channels. J. Hydraul. Eng. 120: 245-253.
  302. Knight D.W. & Shiono K. 1996. River channel and flood- plain hydraulics. In: Anderson M., Walling D. & Bates P. (eds.), Floodplain processes, John Wiley, Chichester. pp. 139-182.
  303. Knighton D. 1984. Fluvial forms and processes, John Wiley, London.
  304. Kouwen N. & Unny T.E. 1973. Flexible roughness in open channels. J. Hydraul. Div. ASCE 99: 713-728.
  305. Lachat B. 1994. Watercourses: conservation, maintenance and management. Planning and management series 2, Council of Europe, Strasbourg.
  306. Lempinen P., Luttinen R. & Pummila A. 1999. Tuusu- lanjoen ympäristöselvitys, Monisteita 61, Uudenmaan ympäristökeskus, Helsinki.
  307. Masterman R. & Thorne C.R. 1992. Predicting influence of bank vegetation on channel capacity. J. Hydraul. Eng. 118: 1052-1058.
  308. Mertens W. 1989. Zur Frage hydraulischer Berechnungen naturnaher Fließgewässer. Wasserwirtschaft 79: 170-179.
  309. Murota A., Fukuhara T. & Sato M. 1984. Turbulence structure in vegetated open channel flows. J. Hydrosc. Hydraul. Eng. 2: 47-61. National Board of Waters 1984. Hydrologiset havainto-ja mittausmenetelmät, Publication of The Water Adminis- tration 47, Helsinki, Finland.
  310. Nuding A. 1991. Fließwiederstandsverhalten in Gerinnen mit Ufergebüsch. Entwicklung eines Fließgewässer mit und ohne Gehölzufer, unter besonderer Berücksichti- gung von Ufergebüsch. Wasserbau-Mitteilungen Nr. 35, Technische Hochschule Darmstadt.
  311. Pasche E. & Rouvé G. 1985. Overbank flow with veg- etatively roughened floodplains. J. Hydraul. Eng. 111: 1262-1278.
  312. Patt H., Jürging P. & Kraus W. 1998. Naturnaher Wasser- bau: Entwicklung und Gestaltung von Fließgewässern, Springer, Berlin.
  313. Schröder R.C.M. 1990. Bestimmung von Rauheiten. In: Schröder R.C.M. (ed.), Hydraulische Methoden zur Erfassung von Rauheiten. Schriften, 92, DVWK, Verlag Paul Parey, Hamburg und Berlin, pp. 1-190.
  314. Yen B.C. 2002. Open channel flow resistance. J. Hydraul. Eng. 128: 20-39.