Final Hydrological and Hydraulic Model

Final Hydrological and Hydraulic Model


Objective and Scope

The objective in the development of the model was to build a preliminary Regional Stormwater

Model (RSM) to represent primary drainage systems focused in the unincorporated areas of the County. In developing the GIS support geodatabases and model, the County will be provided with an engineering analysis tool that provides the following benefits: 

  1. To provide a centralized GIS database of information on contributing areas, drainage storage and conveyance features, and overall stormwater management connectivity;
  2. To provide a regional hydrological and hydraulic model source to evaluate primary drainage systems;
  3. To provide a qualitative level of service assessment of the performance of major drainage conveyance and storage systems which will allow the identification of deficient infrastructure and the prioritization of areas for future improvement;
  4. To provide a basic hydraulic network that can be built upon in the future to facilitate more detailed watershed assessment activities including floodplain delineation, small area retrofits, and surface water assessments;
  5. Based on the results of the regional modeling efforts, recommendations can be made for future model expansion, refinement, calibration, and verification to provide a more detailed representation of drainage features. 

Data Development 

In general, the preliminary RSM was developed in the following manner: 

  • The subbasin delineation and network of the model were based on the information collected during Tasks II and III of the SWMP, namely:
    • Digital Terrain Model data originating from LiDAR based topographical data obtained from the Alachua County Property Appraisers office;
    • Drainage facility inventory data along major roadways collected during the Inventory Task of the SWMP, as well as similar inventory data forroadways and development in the urban census area provided by the Gainesville Clean Water Partnership (GCWP); and
    • Construction plans obtained from ACPW, GCWP, and the FDOT.
  • The model was developed based on the following assumptions:
    1. The model will be regional in structure and focused on connectivity of County watersheds. Network connectivity will be based from USGS National Hydrography Dataset (NHD);
    2. This data will be used to identify major system flooding concerns, identify primary drainage structure deficiencies, and make recommendations regarding future development impacts;
    3. The model results will be used to assess deficiencies from flood stages and conveyance deficiencies, no floodplain mapping will be performed;
    4. The model will be single storm event based, utilizing the SCS curve number method and appropriate locally acceptable rainfall distributions and depths for hydrological analysis;
    5. The model will be analyzed using the ICPR v3 computer program;
    6. Where available survey or plans reference data is not available for primary drainage structures or conveyance features, topographical information will be utilized to estimate drainage patterns and facility characteristics; and
    7. Results will be compared to stormwater facility specific LOS criteria for deficiency evaluation 
      1. Data Collection and Inventory
      2. Watershed Characteristics
      3. Flood Model Methodology
      4. Stormwater Level of Service Analysis
      5. Planning Unit Results
      6. Conclusions and Recommendations