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Assessment of the likely impact of climate change on infrastructure and natural ecosystems of a small watershed in British Columbia : implications for hydraulic infrastructure design and stormwater management Denault, Catherine

Abstract

The stationarity of rainfall statistical parameters is a fundamental assumption in hydraulic infrastructure design. Given the increase in rainfall intensity associated with climate change, this assumption might no longer prove valid. This study examines the possible impacts of climate change on the urban infrastructure and natural ecosystems of a small watershed in British Columbia. The methodology was developed with the purpose of providing simple methods to evaluate drainage system vulnerability to increases in rainfall intensity, and to envisage the potential economical and environmental impacts of climate change. Non-stationarities in rainfall records are first analyzed with linear regression analysis, and the detected trends are extrapolated to build future rainfall scenarios. The Storm Water Management Model (SWMM) is then used to analyze the effects of increased rainfall intensity on the Mission/Wagg Creek system. Anticipated changes in land use and the projected changes in rainfall intensity are included in the simulations to obtain probable future runoff conditions. The total length of undersized stormwater sewers, combined with the total number of culverts found to be surcharging during the simulations, attests to the vulnerability of the infrastructure network. An innovative method is proposed to investigate the environmental impacts of climate change. Using SWMM, climate change equivalent levels of imperviousness are determined. These levels represent the Total Impervious Areas (TIAs) for which the runoff values are equal to the runoff values obtained under climate change conditions. This method allows considering the well-researched impacts of urbanization as likely impacts of climate change. In terms of impacts on the infrastructure, the results of this study indicate that climate change would not create severe impacts in the Mission/Wagg Creek system. The infrastructure in place, with the exception of a few trunk sewers and culverts, has the adequate capacity to handle the runoff generated by the future larger storms. The equivalent levels of imperviousness, however, suggest that the impacts on the natural ecosystems of the creeks could be far more damaging.

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