skip to content

Risk Mapping Assessment and Planning Production and Technical Services

An increase in urban development focused FEMA on flood risk mitigation for the Lake Apopka Basin.
  • Detailed terrain map of the Lake Apopka Basin-Gannett Fleming

    Custom GIS tools were used to evaluate the basin’s complex terrain.

  • An overview of the Lake Apopka Basin study area-Gannett Fleming

    Gannett Fleming performed a detailed review of the H&H analysis within the Lake Apopka Basin.

U.S. Department of Homeland Security/Federal Emergency Management Agency

Orange County, Florida

Our Role
Geographic Information Systems, Hydrology and Hydraulics, Floodplain Mapping, Quality Assurance/Quality Control, Outreach.

135 square miles
In Progress
  • Performed a detailed H&H review of an ICPR model for the Lake Apopka Basin
  • Performed initial floodplain mapping of ICPR results using LiDAR
  • Provided FEMA and community with technical guidance on path forward.

Florida’s third-largest lake, Lake Apopka in Orange County, Florida, was once considered the premier bass fishing location in the world. However, development around the lake has increased the Lake Apopka flood risk. The Federal Emergency Management Agency (FEMA) implemented its Risk Mapping, Assessment, and Planning (Risk MAP) program for the basin to update flood hazards and to develop strategies to help mitigate flooding risks.

Gannett Fleming provided a detailed technical hydrologic and hydraulic (H&H) review of an Interconnected Channel and Pond Routing (ICPR) model covering the Lake Apopka basin within Orange County.

What We Did

Gannett Fleming performed a detailed technical review of an H&H analysis for the Lake Apopka Basin. The H&H analysis was simulated using ICPR stormwater model, originally created in support of a larger effort to develop the Lake Apopka Basin Stormwater Management Master Plan (SWMM) for Orange County.  

Before FEMA agreed to revise the flood hazards based on this model, Gannett Fleming reviewed the hydrologic and hydraulic model input and simulation results for the ICPR model. Model characteristics were reviewed at both a global and local scale. To support the review, custom Geographic Information Systems (GIS) tools were used to analyze the data.  Sub-basins were delineated across the basin, and surrounding lakes, depressions, and riverine reaches were mapped to validate the modeling results. A list of technical comments that resulted from the review were communicated to the community and FEMA. The results from this review determined that the data and modeling are not consistent with FEMA standards and engineering practices, making the model insufficient in updating the FEMA Flood Insurance Rate Maps. 

Key Features

  • Quality assurance/quality control
  • H&H analysis
  • Floodplain mapping
  • Community outreach.

Similar Projects: Dams & Levees: Flood Hazard & Risk Assessment, Security & Safety, Water/Wastewater: Stormwater, Federal: Water Resources, Water/Wastewater