Stormwater Runoff Assessment Under Climate Change Scenarios Using Remote Sensing Products. A Case Study in Piura, Peru

Hydrological assessment of the stormwater runoff is a relevant tool to support sustainable drainage planning decisions. In this research we address the pluvial floods in the city of Piura in northern Peru that frequently present problems of water accumulation which become significant and tragic during the period of the ENSO phenomenon. The analysis considers a surface of 194.6 km2. Climate change scenarios and the impact over stormwater runoff events to the year 2050 were analyzed under the pessimistic scenario RCP8.5 from AR5- IPCC. Peruvian IDESEP-SENAMHI database was used to estimate intensities-duration-frequency (IDF) equations for the study area for 50 and 100 years of return period. Additionally, the IDF equations were defined with uncertainty bands according to global climate models used. Urban catchments were delimited and validated by using two global digital elevation models: SRTM and MERIT at a resolution of 90 meters and were compared using field information. The delimitation of the catchments was obtained with the TauDEM toolbox. Impervious surface percentages in each urban catchment offered a great way to evaluate environmental properties in complex road and street networks related to runoff that can be expressed as the runoff coefficient. For this purpose, a global impervious surface map at a resolution of 30 meters was used. Each one of the basins was analyzed by applying different versions of the rational method with an R computational package designed for this purpose. The results showed a good performance on bigger basins. Information from peak runoff, volumes and incremental percentages for diverse climate scenarios were evaluated with uncertainty bands for showing a clear signal of climate change impact. This information would help decision makers for urban planning face strong climatic events with the awareness and social participation in monitoring the critical urban catchments identified and change community attitudes towards pluvial floods problems.