Optimal Allocation of Ecological Management Practices in a Hilly Urban Watershed

Abstract

Urbanization is increasing at a rapid rate and in many places expanding into the hilly areas, thereby inducing significant alteration in the hydrological response of watershed. In the developing world, the process of urbanization is more often unplanned and disorganized, which results in higher yield of sediment and surface runoff, which manifested itself in the form of hazards like flash flood and landslide. Washing off of pollutants from the urbanized impermeable upper catchment is also causing downstream water quality declination. Therefore, urban developments in hilly watersheds require application of efficient management practices that can handle adverse consequences of urban developments in an ecologically sound and sustainable manner. Such eco-friendly sustainable management practices can be termed as Ecological Management Practices (EMPs). However, the cost, efficiencies, and applicability of EMPs vary widely from place to place depending upon the site condition. Therefore, it is necessary to determine the optimal combination of EMPs that satisfies all requirements at minimum cost. In this study, allocation of EMPs for managing sediment and water yield from hilly urban watershed has been done through an optimization model OPTEMP-LM (OPTimal EMP model with Linear programming for Multiple ownership). The model allocates EMPs in such a way that the undesirable hydrological consequences of urban development can be alleviated in a sustainable manner at minimum possible cost while addressing various other constraints imposed by topography and owner’s choice. The model was applied to a micro watershed of Guwahati, Assam, India with three EMPs, namely: grass, garden and detention pond and was found suitable for the proposed application.