Water modeling for coastal flood planning
Modeling the effects of planned infrastructure and flood mitigation
Why Now?
Coastal communities are facing intense storms and continued growth. To manage flooding, low-lying regions rely on pumps, gates, canals, and detention basins. These systems strongly influence how floods rise and recede, yet they are often missing from watershed-scale models used for planning. Modeling the effects of planned infrastructure and flood mitigation investments is necessary to compare options and ensure sufficient investments are made.
What We Did
The SETx-UIFL research team built a detailed computer model of the Alligator Bayou watershed that includes the full drainage system -canals, pump stations, gates, detention basins, and directly connected impervious areas. The model simulates how rainfall moves across the land, through canals, and into pumps in real time. This allows infrastructure operations and watershed flooding to influence each other, just as they do in the field. This model was used to evaluate current system performance during major storms and to test scenarios such as the proposed expansion of the Halbouty Detention Basin and changes in pump performance under high water conditions.
Who Was Involved?
Drainage District 7 (DD7) staff provided canal maps, pump station capacities, operating practices, engineering plans, and hosted site visits to key pump and gate facilities. Their insights into day-to-day operational constraints and system bottlenecks directly informed how infrastructure was represented in the model. This close collaboration ensured that simulated scenarios reflected real-world conditions and management practices, which strengthened the model’s relevance for planning, design decisions, and future flood response strategies.
Findings
This work brings basin-scale hydrology and localized infrastructure operations into one actionable modeling tool. In Alligator Bayou, we found:
• Explicitly representing pumps, gates, and canals improves model realism and usefulness for operations and capital planning.
• Expanding the Halbouty Detention Basin (~5,000 acre-feet) lowers canal stages both upstream and downstream. The largest benefit is faster post-storm drawdown and reduced ponding in low-lying areas; peak flood levels decrease modestly.
• Pump stations can approach or reach capacity during major storms, increasing flood duration in certain areas.
The infrastructure tools developed in this project are available in open-source platforms (ATS v1.6; Watershed Workflow 1.6) and can support future “what-if” analyses for design and planning decisions.
