Evaluation of a tidal flat sediment nourishment as estuarine management measure
The tidal flats in the Eastern Scheldt tidal basin (The Netherlands) are eroding as a result of the construction of the storm surge barrier. These intertidal areas are important foraging grounds for birds and therefore it is important to mitigate the negative effects of erosion. As a pilot, a small part (20 ha) of the Galgeplaat tidal flat in the middle of the Eastern Scheldt was nourished with 130,000 m3 of sediment in 2008. This paper investigates this tidal flat nourishment using a large set of morphological and ecological monitoring data from 2008 to 2012. The nourishment proved effective in mitigating the negative effects of tidal flat erosion. The elevated tidal flat provides a foraging area for birds that is available for a longer period. The nourished area was relatively stable, giving time for the recovery of benthic macrofauna such that birds can benefit from the longer exposure time. Therefore, we conclude that sediment nourishments are an effective management measure to counteract the negative consequences of tidal flat erosion in the Eastern Scheldt, and have potential for other estuaries worldwide.
Fine sediments in the Oosterschelde tidal basin before and after partial closure
Changes in the budget of fine sediments in the Oosterschelde have been measured. These are related to the partial closure of the tidal basin. Before the engineering works, soil texture of most of the basin was sandy. After the works, unconsolidated fine sediments occurred at several locations throughout the Oosterschelde, mainly in the deeper parts of channels and on musselbeds. Fine sediments accumulate due to the reduction in current velocities. Most of the fine sediment comes from the North Sea; internal sources of fine sediments (primary production and erosion of intertidal flats) are of minor importance. Due to the works, the direction of net transport of fine sediments has changed from an export (before the works) into an import. A qualitative discussion of the underlying processes is presented. The changes in the budget of fine sediments have both positive and negative ecological consequences. Muddy deposits on dike slopes have reduced hard bottom macrozoobenthos. The reduced nutrients input due to reduced fresh water input has not resulted in a reduced primary production because it is counter-balanced by a decrease in turbidity.
Intertidal Deposits: River Mouths, Tidal Flats, and Coastal Lagoons
Intertidal Deposits: River Mouths, Tidal Flats, and Coastal Lagoons combines the authors personal and professional experience with the mass of available literature to present a cohesive overview of intertidal deposits and the widely diverse conditions of their formation worldwide. This includes the strong influence of water movements, climate, sediment particle characteristics, vegetation, fauna, and man. Intertidal areas are important for many reasons both scientifically and economically and recently, a growing concern for conservation of these fragile regions strives to preserve and protect their natural balance. This book, written by an international expert in the field, concentrates on the more important intertidal areas distinguished by size and morphology, tidal range, the degree and type of vegetational cover, the amount and type of benthic fauna, the extent of human exploitation, and the degree of previous study. Discusses the more important intertidal areas, subdivided by tidal range. Includes a series of chapters on the morphology of intertidal areas (including channels and creeks), the composition and structures of intertidal sediments, the processes of sediment transport, deposition and erosion, and the influence of intertidal flora and fauna. Presents separate sections on benthic fauna and microflora, saltmarshes, mangroves, and algal mats and seagrasses. Addresses the influence of man on existing intertidal areas. Provides a short chapter on the Holocene history of intertidal areas.