Kenai Peninsula Flood Plain Mapping Kenai, Alaska

This flood plain mapping project was required to meet both USACE and Federal Emergency Management Agency (FEMA) standards and specifications. We planned the mapping project, and set horizontal and vertical control for the survey. Vertical control was established using conventional leveling methods. Horizontal control was established using static GPS observations.

Our Team Member provided aerial LiDAR data collection over the three work areas. During the LiDAR flights, our surveyors occupied horizontal control in each area with GPS to provide data for post processing the position of the airplane and LiDAR sensor. We also collected RTK GPS positions and elevations over several of the roads in each area for quality control of the LiDAR data.

Our hydrographic surveyors returned to each area to conduct bathymetric surveys in the rivers, and over tidal areas. In addition to the bathymetry, we collected spot topography, per FEMA specifications, to provide Quality Assurance checks of the LiDAR data.

Using software written in-house, we modified the LiDAR data files to enable processing within CARIS hydrographic processing software. CARIS enabled us to see biases within the LiDAR data. With corrected data, TerraSond was able to meet both USACE and FEMA specifications.

Deliverables for this project included all raw and adjusted data, AutoCAD created maps containing contours, and other determined items including polylines around structures and roads. Also delivered was a comprehensive report that included documentation of all phases of the project.

Important aspects of this project were:

• Project management
• Establishing horizontal and vertical control
• Aerial LiDAR mapping
• Single beam bathymetry
• RTK GPS used for most bathymetry and topography
• Custom software written for data management
• Large dataset management
• Comprehensive reporting

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