Stormwater Management for Developing Urban Areas under Precipitation and Urbanization changes: a parsimonious approach

The complexity of the risks associated with urban stormwater management is increasing world-wide, with climate change and rapid urbanization being among the main drivers. Climate change is intensifying extreme precipitation events to magnitudes that severely challenge the capacity of existing urban drainage infrastructures. Concurrently, rapidly increasing urban density, particularly in developing areas, results in expanded impervious surfaces, thereby raising the surface runoff volumes and peaks. This leads to hazards such as urban flooding, which has become more frequent in recent decades across the globe. Literature shows that integrating Nature-Based Solutions (NBS) with traditional Urban Drainage System (UDS) can improve system performance by providing increased water storage capacity, flood and flow reduction, and other associated benefits. This study employs the Python-integrated Storm Water Management Model (PySWMM) to model and simulate an existing UDS in a rapidly urbanizing catchment in Gurugram City, India. The 42 km² catchment is divided into 21 sub-catchments. A non-stationary/stationary rainfall frequency analysis is applied to account for potential precipitation trends across the analyzed urban area. Similarly, a simplified methodology is adopted for evaluating changes in urbanization using openly available datasets. The functionality of the UDS is assessed for the effects of changes in precipitation and urbanization for the near future, both individually and in combination. The modelled urban water system is intervened with different NBS interventions and their combinations to quantify the effectiveness of NBS in minimizing the impacts of climate change and urbanization. The results demonstrate a significant reduction in flooding and peak surface runoff outflows.