Can antecedent moisture conditions modulate the increase in flood risk due to climate change in urban catchments?

Climate change coupled with the current trend in rapid urbanization is increasing the risk of flooding that can cause loss of life and damage to property. Adapting to climate change impacts and flood mitigation has become a life critical factor as well as a severe challenge. Green infrastructure and low impact development methods are common approaches that are increasingly used to address stormwater management in developed environments. The analysis and results of this study show that AMC/IC does impact flood response even in urban developed catchments and that it can significantly impact flood responses during storm events. We show that considering AMC/ICs coupled with changes in seasonal rainfall patterns that are projected for warmer climates in the future can modulate some of the increases in flood risk due to climate change. The prevailing thought is that Antecedent Moisture Conditions (AMCs) have little to no relevance in urban hydrology, particularly in relation to climate change. However, current trends in use of stormwater management methods that depend on local storage and infiltration is increasingly making AMC or Initial Conditions (IC) a factor in urban flooding. Despite this trend there is little available literature that discuss the aspect of AMC/IC that can have an implication on urban flood management. Here, we move towards filling this gap in current literature related to impacts of AMCs in flooding of developed areas by focusing on how possible changes in seasonal rainfall patterns in a warming climate might impact AMC and starting conditions in stormwater Best Management Practices (SWBMPs), and how those changed initial conditions impact flood risk in developed areas. Using a comprehensive hydrologic/hydraulic model of an urban/developed catchment and continuous simulation, we demonstrate the importance of accurately accounting for initial conditions in flood assessments. We consider average summer temperatures based on approximately 70 years of historic data to select warm and cold years. We compare the model results between the warm and cold years as a proxy to look at trends related to a future warming climate.