Storm Sewer Infrastructure Planning with Climate Change Risk: Case Studies from Alexandria VA and Singapore

Storm Sewer Infrastructure Planning with Climate Change Risk: Case Studies from Alexandria VA and Singapore

Laurens van der Tak, CH2M Hill

Infrastructure planners and designers routinely use published standard design criteria to guide the sizing of drainage and wastewater conveyance systems, including drains, canals, interceptors, and wet weather pump stations. Those design criteria are often based on an assumed level of service to prevent flooding, expressed in terms of the storm recurrence interval and water level expected for the given facility. Associated with those target levels of service are design criteria that may include tabular or graphical information on precipitation intensity-duration-frequency (IDF), coupled with prescribed precipitation duration and distribution to use for a given type of facility. Recently a number of jurisdictions have realized their design storms may be based on outdated historical climate information and do not include the potential impact of climate change on IDF curves. Additionally, the designs may not reflect new expectations for levels of service or may not reflect more sophisticated hydrologic and hydraulic modeling tools used by engineers and planners. This presentation will review changes in design criteria to reflect more of a risk-based approach from two case studies, the City of Alexandria Virginia, and Singapore. In Singapore, the lead author was a member of the Expert Panel for Enhancing Flood Protection for Singapore, which reviewed design criteria and methods applied in Singapore. The expert panels’ recommendations will be reviewed and contrasted with a similar effort being undertaken for the City of Alexandria Storm Sewer Capacity Study. Issues such as the effect of spatial and temporal variation of precipitation and how that affects design criteria, as well as historical trends and projected future precipitation patterns will be reviewed.

Keywords

Stormwater design criteria; risk-based level of service; spatial and temporal variation of precipitation; precipitation trends; precipitation intensity, duration, and frequency; climate change.