Lead Scientists, Stormwater Systems Craftwater Engineering, Inc.
Critical conditions are typically prescriptive protection levels defined by watershed managers or agencies to guide stormwater control measure (SCM) implementation and ensure that SCMs are designed to provide a certain level of runoff capture or water quality treatment to a given drainage area. These critical conditions differ by location, usually related to local watershed climate, needs, and goals, and they range from singular design storm events and volumes to longer-term timeseries meant to assess SCM outcomes over a range of watershed conditions. Planners and managers typically map out stormwater management strategies around meeting these critical conditions for individual SCMs or in aggregate at the watershed scale. At these different scales, certain critical conditions may have a biasing effect to the types of SCMs employed, the size of these relative to the drainage areas they manage, and the distribution of SCMs across the watershed. Additionally, different critical conditions might be more appropriate for different SCM applications in new development, redevelopment, or retrofitting watersheds in need of greater protection. This presentation will present the findings of a modeling study using the Upper Los Angeles River as a test case to highlight some of the most sensitive and defining dimensions of these critical conditions and the prescribed solutions they produce to meet the needs of the watershed. Results will demonstrate what needs to be considered when planning at the watershed scale in relation to different critical conditions and which might result in the most robust and resilient SCM systems to meet the full needs of stormwater management for a given watershed.
