Restoration of urban forests to reduce flood susceptibility: A starting point

Abstract

Urban areas are highly vulnerable to a variety of flood types, including river floods. Mapping susceptible areas of a watershed is a key measure to develop an assessment of restoration strategies to protect people from flooding, but it is difficult to pinpoint the best place to start. Studies about flooding in urban areas and priority areas for restoration have been conducted separately; however, the interface between these themes has been less explored. Therefore, this paper presents two methods to develop flood susceptibility maps, as well as priority restoration areas: Areas of Variable Inflow (AVI) and the most Hydrologically Sensitive Areas (HSA+). The AVI calculation was developed using the Topographic Wetness Index (TWI). The HSA + calculation was based on criteria that are among the most used in flood studies, combined using the Analytic Hierarchy Process (AHP). All AVI and HSA+ within Riparian Preservation Areas (RPA) and without vegetation cover were considered priority areas for restoration. AVI occupied 16.6759 km2 (18.63%), with 2.1172 km2 as a priority (3.76% of the RPA). HSA + included 12.4863 km2 (13.95%), with 3.3603 km2 as a priority (5.97% of the RPA). Most AVI and HSA+ were located outside the RPA, which indicates the necessity for additional conservation on the watershed, even though restoration within RPA must be the priority. Both methods may be applied in any watershed, but we indicate that HSA + provides better results since it considers a wider range of criteria. Since flooding events are rising due to climate change, prioritizing restoration efforts becomes indispensable.