BUILDING WITH NATURE: ECODYNAMIC SOLUTIONS FOR THE PROTECTION OF INTERTIDAL HABITATS

摘要

Coastal erosion represents a serious threat along many coastlines, and will become more serious due to human-induced changes and climate change. In the Oosterschelde (SW-Netherlands), intertidal areas disappear at a fast rate after realization of the Delta works. Reduction in tidal flat area and elevation result in loss of valuable habitats and undermine the coastal defense as dikes become less protected from waves and currents. To deal with these threats innovative, cost-efficient and sustainable methods are required. Within the Dutch innovation programme Building with Nature, in cooperation with Rijkswaterstaat Zeeland, we investigate two ecodynamic solutions for the Oosterschelde: (1) biogenic reefs as ecosystem engineers for stabilization of tidal flats, and (2) nourishments for maintaining tidal flats. The biogenic reef solution uses the concept of ecosystem-engineering as promising measure for sustainable coastal protection. Ecosystem engineering (=modification of abiotic environment due to biological activity) is an important mechanism in shaping landscapes. Ecosystem engineers such as oyster reefs are conspicuous habitats that influence tidal flow and wave action and, in doing so, modify patterns of sediment deposition. In particular, we investigate the potential use of oyster reefs in the intertidal zone for stabilization of tidal flats. A small-scale experiment done in 2009 showed promising results and in 2010 a large-scale pilot will be done to test the ecomorphological impact of artificial biogenic reefs and their effectiveness to reduce erosion of intertidal areas. For the nourishment solution, a tidal flat was nourished with 130,000 m~3 of sand in September 2008, covering an area of 15 ha. The ecomorphological effects are monitored and used to learn from the field and to model the impact and effectiveness of nourishments in maintaining intertidal areas. A high-resolution ARGUS-BIO camera system is used for continuous online monitoring through measurements of geomorphology, hydrodynamics, and biological activity. After one year only minor morphological change of the nourishment is observed, and first signs of benthic recovery appeared. In this paper we present the two solutions - biogenic reefs and nourishment - in more detail and show the first results that were derived from the pilot experiments.