In Bennington, Vermont, Milone & MacBroom, Inc.'s geomorphologists have been working to design and implement a floodplain restoration project to reduce flood and erosion hazards of the Roaring Branch. The channel is located on an alluvial fan and consists of large coarse sediment deposits and a braided channel that is highly dynamic. The river has a history of flooding and has been repeatedly confined with berms in an attempt to control the river and reduce the extent of flood damage. This strategy has energized the channel during floods that mobilize the coarse bedload and cause excessive sedimentation at bridges.
Hydrology, hydraulics, and sediment transport analysis were performed using LIDAR, Milone & MacBroom, Inc. survey, and the ArcGIS extension HEC-GeoRAS. A combined approach was selected as the preferred alternative where floodplain creation established sediment deposition areas upstream and away from a bridge, and removal of existing sediments at the bridge helped the channel towards a more natural sediment regime.
The first phase of work will be constructed in summer 2010.