Gila River Indian Community Land Use Action Review Drainage Assessments

Project: Gila River Indian Community Land Use Action Review Drainage Assessments

Client Name: Gila River Indian Community, Land Use Planning and Zoning Department

Key Personnel: Brian Schalk – Project Manager; Hari Raghavan – Project Engineer/Technical Lead

Project Description: The Community Housing Initiative consists of each district preparing for future housing developments in areas that had unknown drainage hazards. To protect future residential structures from the threat of flooding, drainage assessments were prepared to identify existing drainage conditions along with proposed local improvements and estimated construction costs to mitigate adverse drainage impacts. Drainage assessments for Districts 1, 2, 3, and 4. Consisting of seventy-five (75) parcels (tribal land parcel or allotment) proposed for future housing development were completed.

Flood hazard technical information was provided with each of the drainage assessments, which included: flood extents (floodplain); flow magnitude, depth, and velocity; and flood risk rating for residential structures. Flood risk evaluations were used for effective planning of local drainage improvements to help mitigate flooding. FLO-2D hydrologic and hydraulic modeling approach was used to identify potential flood hazards. The modeling effort and results were commensurate with the level of available data collected to construct FLO-2D models. FLO-2D modeling was completed for existing conditions using the 100-year, 6-hour event. The final FLO-2D modeling approach was approved by LUPZ prior to commencement of the modeling effort. Drainage assessments were organized in a technical data notebook (TDN) for ease of reference.

Additional needs and cautions associated with the project were completed as follows:

  • Flood hazard delineations were appropriately mapped based on available topographic data.
  • Base flood elevations (BFEs) in the form of water surface elevation contours were determined to help establish finished floor elevations based on FLO-2D grid-based results.
  • An aggressive schedule was met to complete all drainage assessments within eight (8) weeks after the notice to proceed.