hierarchical optimization approach to watershed land use planning

A hierarchical optimization framework is developed to analyze spatially complex watersheds and to support spatial decision making for land management practices. A watershed is subdivided into smaller spatial units according to its hierarchy, and a three‐level optimization approach determines optimal land allocations at the subarea, catchment, and 30 m cell levels. A storm water runoff simulation model is used to generate peak discharge pseudo data, under different land use patterns. The results are inputs to regression analyses, and the functional relationships between peak discharges and land use variables are estimated as quadratic functions (r2 > 0.90). These functions are used in the optimization models to allocate future land uses to minimize peak discharges at the watershed and subarea outlets. The integrated hydrological land use optimization (IHLUO) model is next used to allocate land uses at the cell level. The results are promising, with a 46% reduction of the peak discharge rate as compared to the rate generated by the current land use pattern. The results provide site‐specific guidelines for land use management and practices at a high spatial resolution (30 m). The proposed methodology is applied to the Old Woman Creek watershed, located in the southwestern basin of Lake Erie (Ohio).