GA-based simulation-optimization approach for designing fish habitat in canal

A GA (Genetic Algorithm)-based simulation-optimization method is presented in order to search for best configurations of blocks located for creating valuable fish habitat in a canal. The habitat condition is evaluated by a habitat suitability index (HSI)-based method considering hydraulic factors such as water depth and velocity. The study area, a section of canal, is discretized into triangular finite elements with nodes, and the two-dimensional simulation of flow is conducted by the finite element method applied to the steady-state shallow water equations. The computed water depth and velocity at each node are then used to evaluate the comprehensive suitability defined as a habitat potential (HP) for the canal using the SI and HSI in the canal section. The simulation part of the developed method comprises the numerical computation of canal flow aiming at evaluation of the HP, whereas the optimization part includes rearrangement of blocks conducted by GA operators. The simulation and optimization are iterated in order to maximize the HP in the canal section. The applicability of the presented simulation-optimization method is demonstrated for a hypothetical ecohydraulic design of spawning area of Ayu (plecoglossus altivelis) in a canal. The demonstrative example shows that the presented method can derive better block placement in the canal section under some conditions on upstream discharge.