ASSESSMENT OF POSSIBLE IMPACTS OF CLIMATE CHANGE IN AN URBAN CATCHMENT¹

Abstract

Stationarity of rainfall statistical parameters is a fundamental assumption in hydraulic infrastructure design that may not be valid in an era of changing climate. This study develops a framework for examining the potential impacts of future increases in short duration rainfall intensity on urban infrastructure and natural ecosystems of small watersheds and demonstrates this approach for the Mission/Wagg Creek watershed in British Columbia, Canada. Nonstationarities in rainfall records are first analyzed with linear regression analysis, and the detected trends are extrapolated to build potential future rainfall scenarios. The Storm Water Management Model (SWMM) is used to analyze the effects of increased rainfall intensity on design peak flows and to assess future drainage infrastructure capacity according to the derived scenarios. While the framework provided herein may be modified for cases in which more complex distributions for rainfall intensity are needed and more sophisticated stormwater management models are available, linear regressions and SWMM are commonly used in practice and are applicable for the Mission/Wagg Creek watershed. Potential future impacts on stream health are assessed using methods based on equivalent total impervious area. In terms of impacts on the drainage infrastructure, the results of this study indicate that increases in short duration rainfall intensity may be expected in the future but that they would not create severe impacts in the Mission/Wagg Creek system. The equivalent levels of imperviousness, however, suggest that the impacts on stream health could be far more damaging.

A review of the potential impacts of climate change on surface water quality

“…The assumption of stationarity of rainfall properties for hydraulic infrastructure design is no longer tenable, so retrofitting or upgrading of drainage capacity may be required (Denault et al, 2006). Adaptation responses must accommodate potential changes in both the frequency of extreme precipitation events of given magnitude, and changes in the severity of events with given return periods.…”

Transição em infraestruturas urbanas de controle pluvial: uma estratégia paisagística de adaptação às mudanças climáticas

“…Contudo, com a contribuição das mudanças climáticas na alteração dos padrões conhecidos de intensidade e frequência das precipitações, esse modelo estacionário de cálculo torna-se inadequado e, se mantido como método utilizado, aumentará a probabilidade de sobrecarga nos sistemas de drenagem urbana e o risco de enchentes. (MAILHOT;DUCHESNE, 2010;DENAULT, MILLAR;LENCE, 2006;GUO, 2006). Considerando esse aumento nos eventos extremos de chuva, apesar das incertezas quanto à magnitude e às variações regionais das mudanças climáticas, algumas cidades e regiões já avaliaram os possíveis impactos das precipitações mais intensas em seus sistemas de drenagem urbana (figura 1).…”

Dynamic neural networks for real-time water level predictions of sewerage systems-covering gauged and ungauged sites

“…The SWMM is a comprehensive hydrological simulation model that is commonly applied to designing the quality and quantity models of runoffs in urban areas (Ackerman and Schiff, 2003;Baffaut and Delleur, 1990;Borah and Bera, 2003;Denault et al, 2006;Maharjan et al, 2009;Tsihrintzis and Hamid, 1998). As understood, even though the RNN can easily build a water level prediction model at the gauged sites, the difficulty in predicting the water levels at an ungauged site is due to its unavailability of real observations for the training and evaluation of a RNN.…”