Environmental Planning and Economics Analysis
Environmental planning, nature-based solutions (NBS), and green stormwater infrastructure (GSI) are a core component of the TSI study because natural systems such as floodplains, wetlands, riparian corridors, and native vegetation provide critical stormwater and flood resilience benefits. Recognizing the interconnected nature of transportation, stormwater, and environmental systems, the TSI approach identifies opportunities to integrate transportation improvements with GSI, floodplain preservation, habitat restoration, and other NBS strategies. It is also important to understand how future growth and development may influence flood risk and associated economic damages, and the relative costs and benefits of different stormwater and flood mitigation strategies over time.
The TSI study team conducted research and environmental screenings to identify where GSI/NBS may support intentional management of stormwater runoff and flood risk.
Research
Research memos identifying existing environmental sustainability efforts and products that could be replicated or adapted within the TSI study area are linked below:
- Green Stormwater Infrastructure/Nature-Based Solutions Memo
- Common Recommendations from the Denton County Greenbelt Plan and regional Watershed Protection Plans Memo
Environmental Screening
Methodology/assessment memos/reports and maps detailing the environmental screening results are linked below:
- Stacking Model Methodology Memo - This document presents the complete methodology used to develop a GIS-based framework to evaluate flood susceptibility, flood vulnerability, and flood control priorities. The maps linked below display these results. The redder areas, and their upstream areas, on the flood control prioritization maps should be considered for implementation of flood control measures.
- Soil and Water Assessment Tool (SWAT) Modeling Report - This document describes the use of the SWAT Model to quantify changes in water yield at the subbasin level under projected land use scenarios and simulates the flood mitigation performance of GSI under three implementation scenarios. The maps linked below display these results.
- Water Yield Increase Map (2016-2070)
- Maximum Potential GSI Coverage Map (2070)
- Water Yield Reduction Map with Maximum GSI Implementation
- Water Yield Reduction Map with 75% GSI Implementation
- Water Yield Reduction Map with 50% GSI Implementation
- Bioretention Report - This document describes the analyses that took place to predict the maximum potential bioretention area in 2045 and 2070 based on 2020 impervious land use. The maps linked below display these results.
- Urban Maximum Potential GSI: Parking Lot Bioretention (2045) Map
- Urban Maximum Potential GSI: Parking Lot Bioretention (2070) Map
- Urban Maximum Potential GSI: Parks and Trails Bioretention (2045) Map
- Urban Maximum Potential GSI: Parks and Trails Bioretention (2070) Map
- Urban Maximum Potential GSI: Sidewalk Bioretention (2045) Map
- Urban Maximum Potential GSI: Sidewalk Bioretention (2070) Map
- Urban Maximum Potential GSI: Vegetated Median Bioretention (2045) Map
- Urban Maximum Potential GSI: Vegetated Median Bioretention (2070) Map
- Environmental Analysis Mitigation Banking Memo – This document integrates a mitigation credit supply-demand analysis with H&H modeling to identify planning-level opportunities where stream and wetland restoration or enhancement can both meet mitigation needs and reduce future flood risk.
Economics
The TSI study team conducted an Economics Analysis to quantify the costs of inaction, assess the economic benefits of stormwater management investments designed to maintain current flow conditions, and compare alternative flood mitigation strategies, including regional detention projects, property buyouts, NBS, and GSI.
The TSI study team also created a GSI Benefit-Cost Tool in Excel to help communities compare different types of GSI and approximate estimates of benefits and costs for GSI in the North Central Texas region. The tool measures lifecycle benefits and costs over a period of 50 years.