Flood-inundation maps for the Hoosic River, North Adams and Williamstown, Massachusetts, from the confluence with the North Branch Hoosic River to the Vermont State line

Abstract

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov/ or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod/ To order this and other USGS information products, visit http://store.usgs.gov/ Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.Suggested citation: Lombard, P.J., and Bent, G.C., 2015, Flood-inundation AbstractA series of eight digital flood-inundation maps were developed for an 8-mile reach of the Hoosic River in North Adams and Williamstown, Massachusetts, by the U.S. Geological Survey (USGS) in cooperation with the Federal Emergency Management Agency and are available at the USGS flood inundation mapping website at http://water.usgs.gov/osw/flood_inundation. The coverage of the maps extends from the confluence with the North Branch Hoosic River to the Vermont State line. Peak flows with 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities were computed for the reach from updated floodfrequency analyses. These peak flows were routed through a onedimensional step-backwater hydraulic model to obtain the corresponding peak water-surface elevations, and to place the tropical storm Irene flood of August 28, 2011 into historical context. The hydraulic model was calibrated by using the current (2014) stagedischarge relation at the USGS streamgage Hoosic River near Williamstown, Massachusetts (01332500), and from documented high-water marks from the tropical storm Irene flood, which had approximately a 1-percent annual exceedance probability.The hydraulic model was used to compute water-surface profiles for flood stages referenced to the streamgage and ranging from 9 feet (ft; 624.45 ft North American Vertical Datum of 1988 [NAVD 1988]), which is near bankfull, to 16.1 ft (631.59 ft NAVD 1988), which exceeds the maximum recorded water level at the streamgage and the National Weather Service major flood stage of 13.0 ft. The mapped stages, from 10.9 to 16.1 ft, were selected to match the stages of flows with annual exceedance probabilities between 20 and 0.2 percent, and thus do not fall at exact 1-ft increments. The simulated water-surface profiles were combined with a geographic information system digital elevation model derived from light detection and ranging (lidar) data having a 0.5-ft vertical accuracy to create a set of flood-inundation maps.The availability of the flood-inundation maps, combined with information regarding current (near real-time) stage from USGS streamgage Hoosic River near Williamstown, and forecasted flood stages from the National Weather Servic...

Tropical storm Irene flood of August 2011 in northwestern Massachusetts

“…The water-surface elevations were compared at 26 selected locations generally upstream and downstream from bridges, dams, and major tributaries (table 7). The simulated water-surface elevations of the 1-percent AEP discharge (Lombard and Bent, 2015a) averaged 0.7 ft higher (median 0.6 ft higher) than the FISs' water-surface elevations. The difference between 1-percent AEP discharge water-surface elevations in Lombard and Bent (2015a) and the FISs ranged from 2.7 ft lower to 7.2 ft higher (table 7).…”

“…The lidar data collected for this study are available as digital elevation model (DEM) data through the Massachusetts Office of Geographic Information System (MassGIS) (2015), and the data accuracy and other information are available from the National Oceanic and Atmospheric Administration (2013). The flood-inundation maps for the Deerfield River, Green River, North River, and Hoosic River can be viewed on the USGS flood-inundation mapping Web site at http://wimcloud.usgs.gov/apps/FIM/ FloodInundationMapper.html, and the flood recovery maps are available as shapefiles with the reports (Lombard and Bent, 2015a;Flynn and others, 2016;Bent and others, 2015;and Lombard and Bent, 2015b, respectively).…”

“…The water-surface elevations of the 1-percent AEP discharge were simulated from hydraulic models for sections of the Deerfield River (Lombard and Bent, 2015b), Green River (Flynn and others, 2016), North River (Bent and others, 2015), and Hoosic River (Lombard and Bent, 2015a). The hydraulic modeling for these studies was completed using the U.S. Army Corps of Engineer (USACE) Hydrologic Engineering Center-River Analysis System (HEC-RAS) model.…”

“…The simulated water-surface elevations of the 1-percent AEP discharge for the Hoosic River determined from the HEC-RAS hydraulic model developed by Lombard and Bent (2015a) were compared with those of the FISs for the town of Williamstown (1983b) and the city of North Adams (1981) from the Massachusetts-Vermont State border in Williamstown upstream to the confluence with the North Branch Hoosic River in the City of North Adams. The water-surface elevations were compared at 26 selected locations generally upstream and downstream from bridges, dams, and major tributaries (table 7).…”

“…Table 7. Comparison of the water-surface elevations for the Hoosic River for the 1-percent annual exceedance probability discharge determined by Lombard and Bent (2015a) with those published in the effective Federal Emergency Management Agency flood insurance studies.…”