Three
Forks Flood Study
Three Forks, Montana
The Three Forks Flood Study
of the Madison and Jefferson Rivers in the vicinity of
Three Forks, Montana was used to create updated FEMA Flood
Insurance Rate Maps. The project consisted of project management
for surveying, creation of base maps and floodplain mapping.
Allied Engineering utilized state-of-the-art software including
HEC-GeoRas and ArcView with 3D Analyst to perform the flood
mapping. The study reach included upstream and downstream
of the junction between the two rivers. Allied’s
client, Joe Van Mullem, performed the hydrologic analysis
and floodplain modeling. The floodplain modeling was performed
with the computer program HEC-RAS and involved complicated
flow spits, levees, ice jamming analysis, and numerous
bridges. This study was completed in 2005.
Key project
elements were automated
geometry extraction and floodplain mapping, compliance
with FEMA Guidelines and specifications for flood hazard
mapping partners, floodplain mapping for an area covering
roughly 7.5 square miles and over 6 miles of river studies,
and over 40 bathymetric cross-sections utilizing
GPS, a boat, and conventional techniques.
