Assessment of environmental restoration plans for a small-scale beach by simulation-based habitat evaluation

In order to assess the effect of environmental restoration plans for a small scale beach called Heda-Mihama, simulation-based habitat evaluation approach is employed. A three-dimensional hydrodynamic model is developed by using the measured topography to reproduce the characteristics of currents around Heda-Mihama. A sediment transport model is also developed to predict the distribution and change of sediment size at the target site. For the assessment of the ecological value of the site, HEP (Habitat Evaluation Procedure) is employed, in which one of the typical species of bivalves is chosen as a target species. Water depth, sediment size, bottom friction velocity are chosen as the environmental factors for the target species. The suitable indices (SI) for each environmental factors are calculated by using the results of hydrodynamic and sediment transport simulations. By using the developed scheme, habitat values are evaluated for the proposed restoration plans and compared to the current values. It is predicted that the removal of the piers will significantly increase the habitat value of the target site. It is because the water current is significantly increased which make the sediment size larger as well as promote the water exchange at the site.