GeoEngineers characterized existing channel morphology and migration type for the Upper Puyallup, White and Carbon rivers
GeoEngineers’ approach includes a LiDAR-processing technique that displays differences in ground elevation relative to the adjacent channel elevation.
Potential migration zones overlaid on aerial photographs of the project area
Pierce County Channel Migration Study
A sophisticated channel analysis helped a county plan for and manage floods.
Pierce County officials were worried that future channel migration on the Upper Puyallup, White and Carbon rivers could damage property and infrastructure. The county asked GeoEngineers to develop a channel migration zone (CMZ) analysis in order to better understand potential river boundaries over the next 50 to 100 years and identify low, moderate and severe migration hazard areas.
Approach
- Reviewed historical aerial photographs, topographic and geologic maps to calculate rates of lateral channel migration and downstream movement of gravel bars
- Characterized existing channel morphology and migration type, and the history of channel migration
- From dated aerial photographs, identified low, medium and high migration hazard areas
- Evaluated potential future erosion sites
- Digitized river channels into geographic information system (GIS) layers with attributes
- Used GIS-based data to evaluate and delineate the width of the CMZ
Results
- Pierce County used the resulting CMZ maps to develop flood hazard plans, floodplain management plans and levee-setback planning.
- Layered GIS maps track river movements from photo year to photo year, aiding the County’s flood hazard monitoring efforts.
- Future GIS-based projects can be added to the County’s GIS database for additional planning.
- Field staff completed site verification in three days.
