Development of a model to assess coastal wetland stability

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The proposed research is directed towards developing a model for the prediction of coastal wetland stability. Over the past three decades, the number of coastal wetlands in Canada has been reduced by over 90 percent as a result of human interference in the coastal zone. It is now recognized that coastal wetlands play an integral role in fostering bio-diversity in the coastal zone, improving local water quality and providing a means of shore protection in erosion prone areas. Very little is known about the factors controlling the stability of coastal wetlands, which include water level fluctuations, incident wave climate, the erosive potential of the waves on the soil matrix in which the plants grow and ice conditions prevalent at the site. The proposed research is directed at quantifying these controlling parameters and developing a model to predict probable wetland stability for a given location. This research will lead to the development of sound design principles for coastal wetlands which can be directly implemented into practise. The research program will utilize field and laboratory studies and numerical modelling techniques. Field studies will be undertaken at three sites to identify typical characteristics under which coastal wetlands thrive. These sites will be instrumented to enable determination of the incident and transmitted wave climate and water level fluctuations at the sites. Wetland growth will be mapped over the course of three growing seasons. Plant geometry, plant densities and plant strength characteristics of various species and the nature of the substrate in which the plants are growing will be documented. Laboratory studies will be undertaken in a wave flume to further evaluate wave transmission through coastal wetlands under controlled conditions. Tests will be conducted to investigate the influence of plant type, plant density, depth of submergence, width of plant bed and incident wave characteristics on wave transmission through the wetland. Finally, a numerical model will be developed which evaluates the hydrodynamics in the wetland and relates this to wetland stability and will include wave interaction with wetland plants, stability of the substrate, water level fluctuations and resistance provided by the plant strength.