Application of PCSWMM to Assess Wastewater Treatment and Urban Flooding Scenarios in Phnom Penh, Cambodia: A Tool to Support Eco-City Planning

Eco-city philosophy and urban sustainability have been increasingly incorporated into planning and policy making. Often, system sustainability and resilience are assessed using a simple index approach, which can be helpful in measuring changes over time or in a comparative evaluation of cities, but is less helpful in guiding specific policy and design decisions. To this end, we illustrate the application of a dynamic water resource model which can complement an index analysis. Specifically, a personal computer (PC) version of the Stormwater Management Model (PCSWMM) was used to explore different wastewater treatment and urban flood management scenarios for Phnom Penh, Cambodia. Currently wastewater in Phnom Penh is treated effectively using sustainable, naturally occurring wetlands. Urban expansion is placing increasing pressure on these wetlands and PCSWMM results showed that infilling of the largest wetland by up to 22% could have a negative impact on treatment, but the system still would function. The alternative of activated sludge treatment is shown to be costly and energy intensive. Impacts of infilling on the large peri-urban community living on the wetland and to other ecosystem services were not assessed. Increased pump capacity at the existing stations would reduce, but not eliminate, local surface flooding. More sustainable, eco-friendly low impact development technologies should be considered in addition to hard engineering to reduce surface flooding.