Assessing the impact of urbanization on flood risk and severity for the Pawtuxet watershed, Rhode Island

Abstract

ABSTRACTCampbell A, Pradhanang SM, Kouhi Anbaran S, Sargent J, Palmer Z, Audette M. 2017. Assessing the impact of urbanization on flood risk and severity for the Pawtuxet watershed, Rhode Island. Lake Reserv Manage. 34:74–87.This study models the Pawtuxet River watershed with the Soil and Water Assessment Tool (SWAT) and high spell analysis to understand the impacts of land use and management on flood events. The watershed is in central Rhode Island and contains the Scituate Reservoir and the southern suburbs of Providence. The area is divided between urban development along Narragansett Bay and forested land cover around the Scituate Reservoir. The model was calibrated and validated to a daily time step. The calibration data was for the entirety of 2010 including a flood event in March and early April, which caused significant damage to the region. The calibrated model had a Nash–Sutcliffe efficiency (NSE) of 0.69. The validation had an NSE of 0.65. The model was run with 3 land use/land cover scenarios: the 2011 statewide LULC as a baseline, increased urbanization around Narragansett Bay, and increased urbanization surrounding the reservoir. In the 2011 model, urban land cover accounted for only 13.49% of the study area. Simulated sub-daily flow for the watershed, at a 5 min time step, was used to understand the potential impact of urbanization on flood events. Each year from 2010 to 2013 was analyzed with high spell analysis; the average high spell volume in 2010 was nearly double all other years. The scenarios with increased urban land use saw an increase in the mean volume of high spells, however there was not an increase in the 2010 floods peak.