Musselshell River Floodplain Study Phase 1 and Phase II: The Musselshell River communities are working with the Federal Emergency Management Agency (FEMA) and the Montana Department of Natural Resources and Conservation (DNRC) to update floodplain maps for the Musselshell River. New floodplain maps will depict the latest, most accurate flood risk data, allowing property owners and communities to understand their flood risk and to protect themselves against flooding.
The Montana Department of Natural Resources and Conservation (DNRC) contracted Pioneer to conduct a bathymetric survey, hydraulic structure assessment, and hydrologic analysis for the Musselshell River Floodplain Study – Phase 1 (2015) to provide the groundwork for scoping and completing future floodplain mapping projects throughout the Musselshell River corridor, and a Phase 2 (2016).
Phase 1. For the first Musselshell River floodplain study, Pioneer conducted a bathymetric survey, hydraulic structure assessment, and hydrologic analysis. This first phase of the Musselshell River floodplain study provided the groundwork for scoping and completing future floodplain mapping projects throughout the Musselshell River corridor. Pioneer completed the following for the Phase 1 activities:
Structure and bathymetric survey for a 10-mile reach near Roundup, Montana
- Surveyed 4 bridges and a diversion structure.
- Completed a bathymetric river survey-73 cross sections surveyed (approximately 7 per mile).
- Integrated bathymetric data into light detection and ranging (LiDAR) topography digital elevation models (DEMs).
Field reconnaissance and hydraulic structure assessment
- Covered 335-mile extent of Musselshell River.
- Assessed 87 structures.
- Compiled in Geographic Information System (GIS) geodatabase.
Hydrologic analysis
- Covered 335-mile extent of Musselshell River.
- Conducted flood frequency analysis for 49 flow change locations (8 gaged, 41 ungaged).
For Phase 2. Phase 2 tasks included hydraulic modeling and floodplain mapping for the 10-mile reach of Musselshell River centered around the community of Roundup, Montana. For this phase, Pioneer developed a hydraulic model and created a hydraulic report and work maps. Also completed was a Letter of Map Revision (LOMR) and GIS information:
- Submit MT-2 LOMR to FEMA.
- Submit 1% and 0.2% annual-chance flood and floodway GIS data for map changes.
All work was conducted to meet Federal Emergency Management Agency (FEMA) standards for detail level analysis.
Tasks involved
- Hydrology
- Bathymetric Survey
- Structure Inventory
- Flood Frequency Analysis
- Floodplain Mapping
- Hydraulic Modeling
- Floodplain Mapping
- LOMR Submittal
