River Corridors (August, 2019)

For a thorough discussion of the purpose, design and management of the Vermont River Corridors dataset, please see the "Vermont DEC Flood Hazard Area and River Corridor Protection Procedures December 5, 2014" http://www.vtwaterquality.org/rivers/docs/FHARCP_12.5.14.pdf . River corridors encompass an area around and adjacent to the present channel where fluvial erosion, channel evolution and down-valley meander migration are most likely to occur. River corridor widths are calculated to represent the narrowest band of valley bottom and riparian land necessary to accommodate the least erosive channel and floodplain geometry (i.e. equilibrium conditions) that would be created and maintained naturally within a given valley setting. River corridors are developed to facilitate ANR’s responsibilities in providing municipalities, regional planning commissions, and Act 250 District Commissions with technical assistance and information concerning river sensitivity and fluvial erosion hazards. Vermont river corridors include areas where active, potentially hazardous river erosion and deposition process have occurred or are likely to occur. These delineations do NOT indicate that areas outside river corridors, particularly those immediately abutting the river or river corridor are free from fluvial erosion hazards.This dataset is part of the “applicable maps” used in conjunction with other best available stream geomorphic data to implement both the Flood Hazard Area and River Corridor “Rule” and “Protection Procedure.” The data will be updated over time as described in the Procedure. The date of the version posted on the Vermont Natural Resource Atlas indicates the most recent update. Users should cite the Creation Date for the version. Data processing was done using ArcGIS 10.x, Spatial Analyst, and Arc Hydro Tools 2.0. Source and digitized data included VT Meander Centerlines (MCLs), VT Reach Break points, VT Hydrography streams, VT 10-meter DEM, VTHYDRODEM, HUC 8 Basins, VT Roads and Railroads, field-verified Valley Walls and Stream Geomorphic Assessment datasets. This 2019 version is a hybrid of Phase I and II levels of detail. River Corridor polygons are divided by subwatershed breaks and by SGA reach/segment breaks. Attributes include SGAT ID, Stream Name, Drainage Area in square miles, Bankfull width in feet, Channel Multiplier, DMS Channel Multiplier, DMS Channel Width, Erosion Power/Risk and Deposition Power/Risk. Major derived datasets include raster and vector valley walls, catchments per stream reach, variable-width MCL buffers, and the final River Corridor. A Frequently-Asked Questions page is available at: http://floodready.vermont.gov/rcfaqThis package also includes streams that have a drainage area between .25 and 2 square miles. Streams were mapped by filtering drainage areas from the VHD accumulation grids. They were then extracted from the grid and vectorized. Linework is for reference only, as it does not match the VHD perfectly. Small streams are given a simple 50-foot setback from top of bank in lieu of a mapped River Corridor.