Low-Scale Foreshore Morphodynamic Processes in the Vicinity of a Tropical Estuary at Honnavar, Central West Coast of India (original) (raw)
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2007
STUDY AREA The tidal inlets along Chennai coast could not maintain equilibrium throughout the year because of reduced tidal prism on the estuarine side due to change in characteristics of controlling parameters such as wind, river flow, wave, tidal prism, inlet geometry, sediment supply, etc., as explained in (1998). The 25 km stretch of coastline, from the Ennore in the south up to the Pulicat Lake inlet in the north is a highly threatened coastal ecosystem, due to the several developmental interventions 1999). In the present study morphodynamics of two tidal inlets namely, Ennore Creek and Pulicat Lake, located on the north of Chennai city, Bay of Bengal coast of India (Figure 1) has been studied.
Environmental Earth Sciences
The Kochi Backwater (KB) is the second largest wetland system in India. It is connected to the sea at Fort Kochi and Munambam (Pallipuram) (30 km north of Kochi). As the tide is forced through two openings, its propagation in the backwater system is very complicated, particularly in the northern arm of the estuary. Using synchronous water level (WL) and current measurements in the KB from a network of stations during 2007–2008, it was convenient to demarcate the northern KB into two distinct regions according to the tidal forcing from the north (Pallipuram) and south (Vallarpadam). This demarcation is useful for computing the propagation speeds of the dominant tidal constituents in the northern branch of the KB with dual opening for opposing tides. WL variations indicated that M2 tide (Principal lunar semidiurnal constituent) dominated in the sea level variance, followed by the K1 constituent (Luni-solar declinational diurnal constituent). The M2 tidal influence was the strongest near the mouth and decayed in the upstream direction. The propagation speed of the M2 tide in the southern estuary was ~3.14 m/s. The ratio of the total annual runoff to the estuarine volume is ~42 that indicates the estuary will be flushed 42 times in a year. KB can be classified as a monsoonal estuary where the river discharge exhibits large seasonal variation.
Seasonal Behaviour of a Shallow Estuary of Lower Cauvery Basin, India
Environmental Research, Engineering and Management, 2012
The effect of bifurcation at the estuary mouth was studied on the measurements of salinity, current and tidal depth in a shallow estuary during spring and neap tides of two different seasons. There was a considerable variation of salinity at the observed stations during the seasons. At the shallowest location of the estuary, salinity, as high as 37 ppt, was observed during the period of zero fresh water discharge. The flushing time of the estuary was higher at its western side compared to the eastern one. The diffusion coefficient was reached by using an advection-diffusion equation. The estuary was classified using a circulation/stratification diagram. Well mixed conditions persisted during pre monsoon and post monsoon in the Muthupet estuary.
Wind-driven estuarine turbidity maxima in Mandovi Estuary, central west coast of India
Journal of Earth System Science, 2009
Systematic studies on the suspended particulate matter (SPM) measured on a seasonal cycle in the Mandovi Estuary, Goa indicate that the average concentrations of SPM at the regular station are ∼ 20 mg/l, 5 mg/l, 19 mg/l . SPM exhibits low-to-moderate correlation with rainfall indicating that SPM is also influenced by other processes. Transect stations reveal that the SPM at sea-end stations of the estuary are at least two orders of magnitude greater than those at the river-end during the monsoon. Estuarine turbidity maximum (ETM) of nearly similar magnitude occurs at the same location in two periods, interrupted by a period with very low SPM concentrations. The ETM occurring in June-September is associated with low salinities; its formation is attributed to the interactions between strong southwesterly winds (5.1-5.6 ms −1 ) and wind-induced waves and tidal currents and, dominant easterly river flow at the mouth of the estuary. The ETM occurring in February-April is associated with high salinity and is conspicuous. The strong NW and SW winds (3.2-3.7 ms −1 ) and wind-driven waves and currents seem to have acted effectively at the mouth of the estuary in developing turbidity maximum. The impact of sea breeze appears nearly same as that of trade winds and cannot be underestimated in sediment resuspension and deposition.
A study was undertaken during May 2017 to monitor the impact of tidal actions on the hydrological parameters of the Hooghly estuary. The water quality reflects the impact of Bay of Bengal (sea) water almost on all the variables as revealed from the significant difference of parameter values in high and low tides (except surface water temperature and K). The 12 selected stations from the upstream to downstream regions exhibited uniformity with respect to surface water temperature. Significant spatial variations (at 5% level of significance) were observed with respect to parameters like surface water salinity, pH, alkalinity, DO, BOD, COD, NO3, PO4, SiO3, extinction coefficient, SO4, Na, K, Cl and total N. Along with tidal influences, the anthropogenic factors contributed by the adjacent cities and towns exert a regulatory influence on parameters like BOD, COD, NO3, PO4, extinction coefficient, SO4 and total N.
International Journal of Remote Sensing Applications, 2015
The Bengal plain is characterized by the presence of an extensive coastal tract bordered by the Bay of Bengal in the south. Two contrasting coastal environments are prevailing in the area, namely; the macro tidal Hooghly estuary in the east; and the mesotidal Midnapore Coastal plain to the west. A morphogenetic study based on the terrain mapping unit (TMU) concept reveals the form-process-material interactions of these two contrasting coastal environments with a possible geo-history model of the coastal Quaternaries. It has been established that the entire process-response system of the coastal tract of the Bengal plain started operating after the rise of sea level around 6000yrs B.P. (i.e., optimum of flandrian transgression) and the Hooghly estuary, the mangrove vegetation plays a significant role as the dominant geomorphic agent in the evolution of the tidal shoals and their eventual accretion to the main landmass resulting in delta progradation. In the present-day scenario, the Hooghly estuary becomes the abandoned part of the Ganga-Brahmaputra delta in India, and is also turning destructive and forming erosional regime in the mesotidal Midnapore coastal area.
2014
The barrier-inlet system along the shoreline of Subarnarekha deltaic coast of Odisha state has most diverse morphologies of any barrier system in Indian coast. The delicate adjustment between wave and tide generated processes on the moderate energy coast allows only slight to moderate changes in either of these processes to result in significant and dynamically developing morphologic responses. Some of the natural phenomena such as cyclones induced opening of tidal inlets across the barrier spits, closure of inlets due to longshore transport of sediment, and changes in sediment input into the coastal zones are the result of responses produced by the interaction of energy levels and availability of materials in the coast. Tidal basin behind the barrier spits of Subarnarekha delta plays a significant role in controlling inlet morphology as well as tidal prisms. The various modifications by development have resulted in important morphodynamic changes in the barrier inlet system. These ...
http://link.springer.com/article/10.1007%2Fs12665-011-1128-3, 2012
Qualitative and quantitative evolution of the Swarna estuary, during the past 38 years (1967–2005), has been analysed by integrating the results of field surveys, satellite images, hydrodynamic modelling and topographic data in GIS context. Significant changes in erosion/accretion patterns of the estuarine banks, inlet configuration and adjacent spits, and origin, morphology, orientation and areal extent of fifteen braided islands have been estimated. Hydrodynamics of the region is studied through modelling, and probable flow pattern that is responsible for morphological changes is discussed. The simulated flow patterns indicate that current speeds are of the order of 10–20 cm/s inside the estuary and of the order of 40 cm/s at the mouth. The Right bank (Rb) of the estuary is subject to net erosion and the Left bank (Lb) is subject to net accretion. On an average, 20–30% of the area of all braided islands would be flooded, if the water level rises by 0.7 to 1.0 m. Islands of this estuary are morphologically very dynamic (migrating towards north, northeast and southwest directions) and subject to net accretion, whereas only one island (i.e., the Padu) has lost its major portion of landmass. A conceptual inverse distance weighted (IDW) interpolation model has been generated and evaluated possible flooding on the estuarine shoals and braided islands, due to heavy rainfall and/or sea-level rise. The model reveals that the possibility of flooding will be higher for those islands which are located close to the Rb than those close to the Lb.
Coastal changes in the perspective of long term evolution of an estuary: Hugli, West Bengal, India
Quaternary Sea Level Variation, Shoreline Displacement and Coastal Environment (Proceedings of International Seminar, INQUA Shoreline Indian Ocean Subcommission, 20–26 Jan 1997, Tamil University, Thanjavur) Editors: V. Rajamanickam & M.J. Tooley, New Academic Publishers, Delhi-110002, pp 103–115, 2000
Set in the western edge of the abandoned and eroding western Ganga–Brahmaputra delta, the Hugli is a flood dominated macrotidal estuary and a sediment sink. Comparative study of maps and images between 1851-55 and 1997 reveal that while progressive accretion or cyclic accretion and erosion characterise its non-reclaimed tidal islets, mainly erosion predominates in the reclaimed islands and estuary margins. Dredging and embankment repairing are regularly needed to sustain its navigational channels and to prevent bank erosion. For maintenance of morphological steady state, length of a resonant macrotidal estuary, like the Hugli, tends to equal 25 per cent of the wavelength of the tide entering into it. The tidal wavelength, in turn, depends critically upon the mean depth of the estuary—any alteration of which throws the estuary out of equilibrium. The hydrographic charts of 1904-05 and 1988-92 indicate that this equals 17 per cent in the Hugli, explaining the coastal erosion and in-channel siltation seen there. A rise in the future sea level will lead to an increase in the mean depth of the estuary and remove it even further from the steady state condition. In view of this, controlled retreat from its reclaimed islands and marginal areas and relocation of the resident population should be seriously considered for wetland restoration. These, however, are not easy tasks because of the high population density and high growth rate of population in the interior areas.