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Papers by Willem E Van Duin
The Frisian islands (Southern North Sea) have extensive island tails, i.e. the entire downdrift s... more The Frisian islands (Southern North Sea) have extensive island tails, i.e. the entire downdrift side of an island consisting of salt marshes, dunes, beaches and beach plains, and green beaches. Currently, large parts of these tails are ageing and losing dynamics, partly due to human influence. This may mean a loss of young stages on the long term, and current management is not enough to counteract this. To aid the development of new interventions aiming at (re)introducing natural dynamics, a conceptual model of island-tail development under natural and disturbed conditions was developed, based on existing data, field visits and literature. The development of an island tail follows the general pattern of biogeomorphic succession. The first phase consists of a bare beach plain. In the second phase, embryonic dunes form. In the third phase, green beaches, dunes and salt marshes form, including drainage by creeks and washovers. In the fourth phase, vegetation succession continues and th...
In de Waddenzee liggen langs de noordkust van het vasteland van Groningen en Friesland 6000 ha vo... more In de Waddenzee liggen langs de noordkust van het vasteland van Groningen en Friesland 6000 ha voormalige landaanwinningswerken. Door middel van sturing van de natuurlijke processen zijn daarin halfnatuurlijke kwelders gevormd. De kwelderwerken zijn door middel van rijshoutdammen en begreppeling gecreeerd en de kweldervegetatie heeft zich natuurlijk gevestigd. Uit de praktijk van het natuurbeheer is gebleken dat dergelijke half-natuurlijke landschappen het beste in stand worden gehouden door een beheer dat aansluit bij de traditionele methoden waardoor ze zijn ontstaan (Westhoff 1949, 1971). Zonder de vroegere werken zouden de vastelandkwelders er nu niet zijn en zonder werken nu zouden deze kwelders weer verdwijnen.
Journal of Coastal Conservation, 2016
Earth Surface Processes and Landforms, 2016
The growth and decline of salt marshes may be the result of various interacting biogeomorphic pro... more The growth and decline of salt marshes may be the result of various interacting biogeomorphic processes and external factors. We present a case study of the Mokbaai on the Wadden island of Texel, where we assess the relative importance and the interaction between the biogeomorphic processes and various disturbances. We analysed changes in vegetation composition in the salt marsh and sedimentation-erosion patterns of the adjoining intertidal flat over a 30-year period. Vegetation underwent regression in the lower parts of the marsh, i.e. the low marsh zone changed into pioneer zone. Comparing elevation measurements from 2013 and 1983 showed that the adjoining intertidal flats eroded 15-25 cm. Maintenance dredging of a nearby harbour might negatively impact the sediment balance indicating that the regression of the lower parts of the salt marsh is caused by a lack of sediment. Simultaneously, a change in the local hydrology led to vegetation succession into high and brackish salt marsh, increased organic sediment production and consequently cliff formation. The results from this case study show that, even in a relatively small salt marsh, changes in external factors may set in motion a series of biogeomorphic processes and feedbacks, leading to locally contrasting trends in spatiotemporal development.
IMARES is onderdeel van Stichting DLO KvK nr. 09098104, IMARES BTW nr. NL 8113.83.696.B16 De Dire... more IMARES is onderdeel van Stichting DLO KvK nr. 09098104, IMARES BTW nr. NL 8113.83.696.B16 De Directie van IMARES is niet aansprakelijk voor gevolgschade, noch voor schade welke voortvloeit uit toepassingen van de resultaten van werkzaamheden of andere gegevens verkregen van IMARES; opdrachtgever vrijwaart IMARES van aanspraken van derden in verband met deze toepassing. Dit rapport is vervaardigd op verzoek van de opdrachtgever hierboven aangegeven en is zijn eigendom. Niets uit dit rapport mag weergegeven en/of gepubliceerd worden, gefotokopieerd of op enige andere manier gebruikt worden zonder schriftelijke toestemming.
De Directie van IMARES is niet aansprakelijk voor gevolgschade, noch voor schade welke voortvloei... more De Directie van IMARES is niet aansprakelijk voor gevolgschade, noch voor schade welke voortvloeit uit toepassingen van de resultaten van werkzaamheden of andere gegevens verkregen van IMARES; opdrachtgever vrijwaart IMARES van aanspraken van derden in verband met deze toepassing.
Ecological Restoration of Aquatic and Semi-Aquatic Ecosystems in the Netherlands (NW Europe), 2002
Dit rapport beschrijft een ontwerp van een ecotopenstelsel voor de Nederlandse kustwateren met ee... more Dit rapport beschrijft een ontwerp van een ecotopenstelsel voor de Nederlandse kustwateren met een indeling van 28 sublitorale, litorale en supralitorale ecotopen met de fysische parameters diepteligging (drie klassen), droogvaltijd (vier klassen), overspoelingsfrequentie (vijf klassen), dynamiek (drie klassen), substraat (vijf klassen), zoutgehalte (twee klassen) en een biologische parameter voor mosselbanken en zeegrasvelden. Van alle ecotopen wordt de ligging en ecologische inhoud beschreven. De aansluiting met de EUNIS Marine Habitat Classification, het Benedenrivierecotopenstelsel en een classificatie van terrestrische kustbroedvogelecotopen wordt besproken. Voor validatie en kalibratie wordt een canonische correspondentieanalyse voorgesteld, allereerst met een beperkte gegevensset.
This report concerns the eco-morphologic processes in the Wadden Sea and the Holland/Zeeland delt... more This report concerns the eco-morphologic processes in the Wadden Sea and the Holland/Zeeland delta. It is an inventory report on the managerial questions related to ecomorphology, on the ecological and morphological processes relevant for eco-morphology and on the ecological-morphological interactions. The inventory is based on existing experience within the eco-morphological team: many of its members have been involved in previous projects with an eco-morphological component. The eco-morphological team consists of personnel from:
Ecological Restoration of Aquatic and Semi-Aquatic Ecosystems in the Netherlands (NW Europe), 2002
The conquest of land from the sea has been a long tradition in the Netherlands. When salt marshes... more The conquest of land from the sea has been a long tradition in the Netherlands. When salt marshes were high enough, they were embanked when it was economically feasible, and transformed into intensively exploited agricultural land. This resulted in the transformation of halophytic communities to glycophytic communities. Often as an alternative, a low levee, a summerdike was built, which greatly reduced the flooding frequency of the landward summerpolder, hence creating a sedimentation deficit therein. Such summerpolders now cover 1200 ha in the Netherlands, 2100 ha in NW-Germany and small areas in England. Due to continuous embankments, the present salt-marsh area is relatively small with respect to the tidal basins. Discussions have been started how to increase the salt-marsh area. Two options will be discussed, firstly de-embankment of summerpolders and maintenance of the protective seawall, secondly increase of the effects of saline seepage behind the seawall by top soil removal. Both options include the restoration of salt-marsh communities (target communities) in intensively agriculturally exploited sites that have been salt marshes before. From the few examples abroad and experiments it is discussed (1) to which extent the sedimentation deficit in summerpolders could be compensated for, (2) if the soil seed bank is likely to contribute to re-establishment of salt-marsh communities, (3) if the dispersal of propagules of halophytic plants will be possible by hydrochory when the summerdike is breached, (4) to what extent is dispersal by endozoochory through waterfowl important in case re-establishment in a saline seepage area behind the seawall without open connection to the sea is envisaged. Two case studies of de-embanked summerpolders in the Netherlands revealed that the sedimentation deficit can be counteracted by rapid sedimentation, provided enough transport is possible from the foreshore. Dispersal by incoming tidal water from the nearby salt-marsh source area into the target area is possible for many salt-marsh plant species. The rate of success seems to depend on the relative position of source area and target area. A case study in a saline seepage area after top soil removal in the Netherlands, showed that the number of viable seeds dispersed by droppings from waterfowl is limited. Hence the possibilities for restoration of inland halophytic plant communities seem much lower than after de-embankment of summerpolders.
ABSTRACT In the Wadden Sea, embankments for both agricultural purposes and coastal protection hav... more ABSTRACT In the Wadden Sea, embankments for both agricultural purposes and coastal protection have caused a major loss of mainland salt marshes; their present extent being limited compared to historic reference values. To ameliorate this situation, some 1100 ha of summer polders in Noard-Fryslân Bûtendyks are being restored to salt marsh. By its extent, this is the most important restoration site for salt marshes in Europe. In 2001, the first polder of 135 ha was de-embanked. In order to evaluate the project ecologically, a five-year monitoring programme was launched. Tidal influence in the summer polder was restored by the construction of artificial creeks that were connected to existing creeks in the fronting salt marsh via three breaches in the summer bank. Where these creeks were oversized they rapidly filled with sediment. Surface-elevation change was highest near the breaches and the artificial creeks. In exclosures, surface-elevation change was higher than in grazed areas. Trampling by cattle and horses may have caused some erosion and soil compaction in the grazed area. Sedimentation in the adjacent salt marsh was not affected by the de-embankment. Increase of soil salinity in the restoration site was relatively slow; it’s still somewhat lower than the reference value of the adjacent marsh. Halophytes, however, rapidly invaded the area at the expense of less salt-tolerant plant species. Based on vegetation data, the project appeared to be successful within a couple of years after de- embankment. In grazed areas, the number of target plant species was higher compared to ungrazed control areas. Non-grazed areas had a low biodiversity and were often dominated by Elymus repens. With an increasing salt influence this species most likely will be replaced by E. athericus. The shift in vegetation had no clear effect on breeding birds in the area. In autumn the number of foraging geese decreased. It is expected, however, that this is only a temporary effect. When the saline vegetation shifts more towards Puccinellia maritima over the years, the restoration site will become attractive again for geese. In spring the use of the site increased from the start of the de-embankment on. A comparison with a few other restoration projects in Europe was made to clarify the success. Level to the tidal frame, sediment availability, tidal exchange, drainage, source area for target species and grazing management all were important factors for a rapid development of the saline vegetation
Dit rapport beschrijft een ontwerp van een ecotopenstelsel voor de Nederlandse kustwateren met ee... more Dit rapport beschrijft een ontwerp van een ecotopenstelsel voor de Nederlandse kustwateren met een indeling van 28 sublitorale, litorale en supralitorale ecotopen met de fysische parameters diepteligging (drie klassen), droogvaltijd (vier klassen), overspoelingsfrequentie (vijf klassen), dynamiek (drie klassen), substraat (vijf klassen), zoutgehalte (twee klassen) en een biologische parameter voor mosselbanken en zeegrasvelden. Van alle ecotopen wordt de ligging en ecologische inhoud beschreven. De aansluiting met de EUNIS Marine Habitat Classification, het Benedenrivierecotopenstelsel en een classificatie van terrestrische kustbroedvogelecotopen wordt besproken. Voor validatie en kalibratie wordt een canonische correspondentieanalyse voorgesteld, allereerst met een beperkte gegevensset.
The Frisian islands (Southern North Sea) have extensive island tails, i.e. the entire downdrift s... more The Frisian islands (Southern North Sea) have extensive island tails, i.e. the entire downdrift side of an island consisting of salt marshes, dunes, beaches and beach plains, and green beaches. Currently, large parts of these tails are ageing and losing dynamics, partly due to human influence. This may mean a loss of young stages on the long term, and current management is not enough to counteract this. To aid the development of new interventions aiming at (re)introducing natural dynamics, a conceptual model of island-tail development under natural and disturbed conditions was developed, based on existing data, field visits and literature. The development of an island tail follows the general pattern of biogeomorphic succession. The first phase consists of a bare beach plain. In the second phase, embryonic dunes form. In the third phase, green beaches, dunes and salt marshes form, including drainage by creeks and washovers. In the fourth phase, vegetation succession continues and th...
In de Waddenzee liggen langs de noordkust van het vasteland van Groningen en Friesland 6000 ha vo... more In de Waddenzee liggen langs de noordkust van het vasteland van Groningen en Friesland 6000 ha voormalige landaanwinningswerken. Door middel van sturing van de natuurlijke processen zijn daarin halfnatuurlijke kwelders gevormd. De kwelderwerken zijn door middel van rijshoutdammen en begreppeling gecreeerd en de kweldervegetatie heeft zich natuurlijk gevestigd. Uit de praktijk van het natuurbeheer is gebleken dat dergelijke half-natuurlijke landschappen het beste in stand worden gehouden door een beheer dat aansluit bij de traditionele methoden waardoor ze zijn ontstaan (Westhoff 1949, 1971). Zonder de vroegere werken zouden de vastelandkwelders er nu niet zijn en zonder werken nu zouden deze kwelders weer verdwijnen.
Journal of Coastal Conservation, 2016
Earth Surface Processes and Landforms, 2016
The growth and decline of salt marshes may be the result of various interacting biogeomorphic pro... more The growth and decline of salt marshes may be the result of various interacting biogeomorphic processes and external factors. We present a case study of the Mokbaai on the Wadden island of Texel, where we assess the relative importance and the interaction between the biogeomorphic processes and various disturbances. We analysed changes in vegetation composition in the salt marsh and sedimentation-erosion patterns of the adjoining intertidal flat over a 30-year period. Vegetation underwent regression in the lower parts of the marsh, i.e. the low marsh zone changed into pioneer zone. Comparing elevation measurements from 2013 and 1983 showed that the adjoining intertidal flats eroded 15-25 cm. Maintenance dredging of a nearby harbour might negatively impact the sediment balance indicating that the regression of the lower parts of the salt marsh is caused by a lack of sediment. Simultaneously, a change in the local hydrology led to vegetation succession into high and brackish salt marsh, increased organic sediment production and consequently cliff formation. The results from this case study show that, even in a relatively small salt marsh, changes in external factors may set in motion a series of biogeomorphic processes and feedbacks, leading to locally contrasting trends in spatiotemporal development.
IMARES is onderdeel van Stichting DLO KvK nr. 09098104, IMARES BTW nr. NL 8113.83.696.B16 De Dire... more IMARES is onderdeel van Stichting DLO KvK nr. 09098104, IMARES BTW nr. NL 8113.83.696.B16 De Directie van IMARES is niet aansprakelijk voor gevolgschade, noch voor schade welke voortvloeit uit toepassingen van de resultaten van werkzaamheden of andere gegevens verkregen van IMARES; opdrachtgever vrijwaart IMARES van aanspraken van derden in verband met deze toepassing. Dit rapport is vervaardigd op verzoek van de opdrachtgever hierboven aangegeven en is zijn eigendom. Niets uit dit rapport mag weergegeven en/of gepubliceerd worden, gefotokopieerd of op enige andere manier gebruikt worden zonder schriftelijke toestemming.
De Directie van IMARES is niet aansprakelijk voor gevolgschade, noch voor schade welke voortvloei... more De Directie van IMARES is niet aansprakelijk voor gevolgschade, noch voor schade welke voortvloeit uit toepassingen van de resultaten van werkzaamheden of andere gegevens verkregen van IMARES; opdrachtgever vrijwaart IMARES van aanspraken van derden in verband met deze toepassing.
Ecological Restoration of Aquatic and Semi-Aquatic Ecosystems in the Netherlands (NW Europe), 2002
Dit rapport beschrijft een ontwerp van een ecotopenstelsel voor de Nederlandse kustwateren met ee... more Dit rapport beschrijft een ontwerp van een ecotopenstelsel voor de Nederlandse kustwateren met een indeling van 28 sublitorale, litorale en supralitorale ecotopen met de fysische parameters diepteligging (drie klassen), droogvaltijd (vier klassen), overspoelingsfrequentie (vijf klassen), dynamiek (drie klassen), substraat (vijf klassen), zoutgehalte (twee klassen) en een biologische parameter voor mosselbanken en zeegrasvelden. Van alle ecotopen wordt de ligging en ecologische inhoud beschreven. De aansluiting met de EUNIS Marine Habitat Classification, het Benedenrivierecotopenstelsel en een classificatie van terrestrische kustbroedvogelecotopen wordt besproken. Voor validatie en kalibratie wordt een canonische correspondentieanalyse voorgesteld, allereerst met een beperkte gegevensset.
This report concerns the eco-morphologic processes in the Wadden Sea and the Holland/Zeeland delt... more This report concerns the eco-morphologic processes in the Wadden Sea and the Holland/Zeeland delta. It is an inventory report on the managerial questions related to ecomorphology, on the ecological and morphological processes relevant for eco-morphology and on the ecological-morphological interactions. The inventory is based on existing experience within the eco-morphological team: many of its members have been involved in previous projects with an eco-morphological component. The eco-morphological team consists of personnel from:
Ecological Restoration of Aquatic and Semi-Aquatic Ecosystems in the Netherlands (NW Europe), 2002
The conquest of land from the sea has been a long tradition in the Netherlands. When salt marshes... more The conquest of land from the sea has been a long tradition in the Netherlands. When salt marshes were high enough, they were embanked when it was economically feasible, and transformed into intensively exploited agricultural land. This resulted in the transformation of halophytic communities to glycophytic communities. Often as an alternative, a low levee, a summerdike was built, which greatly reduced the flooding frequency of the landward summerpolder, hence creating a sedimentation deficit therein. Such summerpolders now cover 1200 ha in the Netherlands, 2100 ha in NW-Germany and small areas in England. Due to continuous embankments, the present salt-marsh area is relatively small with respect to the tidal basins. Discussions have been started how to increase the salt-marsh area. Two options will be discussed, firstly de-embankment of summerpolders and maintenance of the protective seawall, secondly increase of the effects of saline seepage behind the seawall by top soil removal. Both options include the restoration of salt-marsh communities (target communities) in intensively agriculturally exploited sites that have been salt marshes before. From the few examples abroad and experiments it is discussed (1) to which extent the sedimentation deficit in summerpolders could be compensated for, (2) if the soil seed bank is likely to contribute to re-establishment of salt-marsh communities, (3) if the dispersal of propagules of halophytic plants will be possible by hydrochory when the summerdike is breached, (4) to what extent is dispersal by endozoochory through waterfowl important in case re-establishment in a saline seepage area behind the seawall without open connection to the sea is envisaged. Two case studies of de-embanked summerpolders in the Netherlands revealed that the sedimentation deficit can be counteracted by rapid sedimentation, provided enough transport is possible from the foreshore. Dispersal by incoming tidal water from the nearby salt-marsh source area into the target area is possible for many salt-marsh plant species. The rate of success seems to depend on the relative position of source area and target area. A case study in a saline seepage area after top soil removal in the Netherlands, showed that the number of viable seeds dispersed by droppings from waterfowl is limited. Hence the possibilities for restoration of inland halophytic plant communities seem much lower than after de-embankment of summerpolders.
ABSTRACT In the Wadden Sea, embankments for both agricultural purposes and coastal protection hav... more ABSTRACT In the Wadden Sea, embankments for both agricultural purposes and coastal protection have caused a major loss of mainland salt marshes; their present extent being limited compared to historic reference values. To ameliorate this situation, some 1100 ha of summer polders in Noard-Fryslân Bûtendyks are being restored to salt marsh. By its extent, this is the most important restoration site for salt marshes in Europe. In 2001, the first polder of 135 ha was de-embanked. In order to evaluate the project ecologically, a five-year monitoring programme was launched. Tidal influence in the summer polder was restored by the construction of artificial creeks that were connected to existing creeks in the fronting salt marsh via three breaches in the summer bank. Where these creeks were oversized they rapidly filled with sediment. Surface-elevation change was highest near the breaches and the artificial creeks. In exclosures, surface-elevation change was higher than in grazed areas. Trampling by cattle and horses may have caused some erosion and soil compaction in the grazed area. Sedimentation in the adjacent salt marsh was not affected by the de-embankment. Increase of soil salinity in the restoration site was relatively slow; it’s still somewhat lower than the reference value of the adjacent marsh. Halophytes, however, rapidly invaded the area at the expense of less salt-tolerant plant species. Based on vegetation data, the project appeared to be successful within a couple of years after de- embankment. In grazed areas, the number of target plant species was higher compared to ungrazed control areas. Non-grazed areas had a low biodiversity and were often dominated by Elymus repens. With an increasing salt influence this species most likely will be replaced by E. athericus. The shift in vegetation had no clear effect on breeding birds in the area. In autumn the number of foraging geese decreased. It is expected, however, that this is only a temporary effect. When the saline vegetation shifts more towards Puccinellia maritima over the years, the restoration site will become attractive again for geese. In spring the use of the site increased from the start of the de-embankment on. A comparison with a few other restoration projects in Europe was made to clarify the success. Level to the tidal frame, sediment availability, tidal exchange, drainage, source area for target species and grazing management all were important factors for a rapid development of the saline vegetation
Dit rapport beschrijft een ontwerp van een ecotopenstelsel voor de Nederlandse kustwateren met ee... more Dit rapport beschrijft een ontwerp van een ecotopenstelsel voor de Nederlandse kustwateren met een indeling van 28 sublitorale, litorale en supralitorale ecotopen met de fysische parameters diepteligging (drie klassen), droogvaltijd (vier klassen), overspoelingsfrequentie (vijf klassen), dynamiek (drie klassen), substraat (vijf klassen), zoutgehalte (twee klassen) en een biologische parameter voor mosselbanken en zeegrasvelden. Van alle ecotopen wordt de ligging en ecologische inhoud beschreven. De aansluiting met de EUNIS Marine Habitat Classification, het Benedenrivierecotopenstelsel en een classificatie van terrestrische kustbroedvogelecotopen wordt besproken. Voor validatie en kalibratie wordt een canonische correspondentieanalyse voorgesteld, allereerst met een beperkte gegevensset.