Systematic planning of stormwater collection system improvement for current and climate change scenarios in the city of Dallas

Abstract:

In the city of Dallas, based on a 2017 collaborative analysis, urban water management, urban heat & air quality, and loss of green space, have been identified as the key environmental health challenges. A systematic approach to prioritize different locations in the city for stormwater improvement projects is needed. This study aims at prioritizing the areas in the city of Dallas based on the performance of the stormwater system to various design storms. In this project, the stormwater network of the most flood- prone watersheds in the city of Dallas were modeled. Hydraulic and hydrologic data for the watersheds was collected using publicly accessible sewer maps and design specifications available in the city of Dallas archives. In doing so, the SWWM 5.0 models were constructed to mimic the hydrologic stormwater flows during the 2, 10, and 100-year current and climate change projected design storms. The climate change projections were based on RCP 8.5 scenario using CMIP 5 model. The simulation results showed that up to 35% of inlets within the seven priority watersheds will be overflown during the 100-year storm significantly. The results also showed that with climate change projection additional 6%- 62% of inlets in the watersheds will be overflown. By recognizing overflown junctions, contributing opportunity subwatersheds to those inlets are also identified for prioritization of stormwater projects. Depending on the watershed, opportunity subwatershed varied from from 15% to 80% of the total area. Interestingly, after accounting for climate change projection, the results showed a marginal increase of maximum 7% in the total opportunity area for the watersheds, highlighting the fact that the current 100-year storm would suffice for design criteria in Dallas. Such subwatersheds are high priority candidates for any stormwater investment projects in the city providing a map for decision-makers to further guide their investments.