Utilizing Modeling Tools for Resilient Urban Stream Restoration
Megan Long
Black & Veatch
Tampa, FL
Authors: Megan Long, John Kiefer
Urban streams drain highly altered watersheds with increased impervious area leading to intensification of stormwater runoff, ditching and draining impacting baseflow, and complex subsurface stormwater networks, bypass canals, and water management structures altering the quantity and timing of water delivered downstream. Removal of natural buffering mechanisms along with location of large populations and infrastructure in or along floodplains make urban streams especially vulnerable to impacts from storm intensification under a changing climate.
Stream restoration design relies heavily on empirical relationships derived by studying comparable streams formed under natural, historic conditions, which may not fully capture the altered mechanics of urbanized conditions. Most regional curves used to design channel and floodplain geometry are a function of drainage area, which may not be driven solely by gravity and topography in urban watersheds. Hydraulic & Hydrologic (H&H) modeling tools can be used to estimate more accurate contributing drainage areas in complex urban watersheds and to compare key geomorphic variables predicted by natural regional curves versus simulated urban conditions. These model results inform stream restoration designs with enlarged riparian floodplains which are resilient to runoff intensification from urban and climate impacts.
H&H models are also used to simulate storm events and screen designs for flooding impacts. In addition to standard storm events required for permitting, H&H models can include predicted future intensified storm scenarios or back-to-back severe weather events. Stream designs can be iterated with modeling results to optimize channel and floodplain geometries that prioritize meeting existing and future designated levels of service, but that also give consideration to minimizing the required footprint in urban areas where many interested parties compete for space and funding.
This presentation will illustrate these concepts using examples from stream restoration projects performed by our team in Florida and discuss how lessons learned in Florida are portable to other regions.
About Megan Long
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