U.S. Geological Survey (USGS) 20150801 vector digital data Reston, Virginia U.S. Geological Survey (USGS) A series of two digital floodplain maps were developed for a 30-mile reach of the Deerfield River in Franklin County, Massachusetts by the U.S. Geological Survey (USGS) in cooperation with the Federal Emergency Management Agency (FEMA). The coverage of the maps extends from the confluence with Cold River to the confluence with Connecticut River. Peakflows with 1- and 0.2-percent annual exceedance probabilities (AEPs) were computed for the reach from updated flood-frequency analyses. These peak flows were routed through a one-dimensional step-backwater hydraulic model to obtain the corresponding peak-water-surface elevations, and to place the tropical storm Irene flood (August 28, 2011) into historical context. The simulated water-surface profiles were combined with a geographic information system (GIS) digital elevation model (DEM) derived from light detection and ranging (lidar) data having a 0.5-foot (ft) vertical accuracy to create a set of flood-inundation maps. These maps delineate the areal extent and depth of flooding corresponding to the selected flood events. This dataset contains the results of the development of a hydraulic model for a 30-mile reach of the Deerfield River in Franklin County, Massachusetts, from the confluence with Cold River to the confluence with Connecticut River and includes the application of flow frequency analyses to the hydraulic model and the creation of a series of flood-inundation maps for the modeled section of the river. 20150801 publication date Complete None planned -72.94 -72.58 42.65 42.51 ISO 19115 Topic Category environment inlandWaters None STATE MA STATE Massachusetts COUNTY Franklin County RIVER Deerfield River COMMUNITY Buckland COMMUNITY Charlemont COMMUNITY Conway COMMUNITY Deerfield COMMUNITY Greenfield COMMUNITY Shelburne None Acknowledgement of the Federal Emergency Management Agency would be appreciated in products derived from these data. ArcGIS 10.1 U.S. Geological Survey (USGS) 2015XXXX map Reston, Virginia U.S. Geological Survey (USGS) http://water.usgs.gov/osw/flood_inundation/ Log Pearson type III flood frequency analyses and a modification of this method, the expected moments algorithm, combined with regional regression estimates are used to compute flows at different locations throughout the reach and for different recurrence intervals (for example, the 1-percent AEP (100-year) event and the 0.2-percent AEP (500-year) event). Computed flows are compared with historic data and flows established in previous hydrologic investigations to ensure reasonableness. Flows exiting the system are carefully analyzed. At a given location flows for longer recurrence intervals are larger. Flows are computed at different locations of the study area. The methods and models used are described in the report. Assumptions and special considerations are also clearly stated in the report. Flows previously determined in other studies or hydrologic investigations are used for comparison. Computed flows are compared with historic flooding data. U.S. Geological Survey 20130930 http://waterdata.usgs.gov/nwis/uv/?site_no=01170000 online 19411001 20130930 publication date FLOW-GAGE1 Historical flow data for the Deerfield River near West Deerfield, MA, for use in flood-frequency analysis U.S. Geological Survey 20130930 http://waterdata.usgs.gov/nwis/uv/?site_no=01168500 online 19141001 20130930 publication date FLOW-GAGE2 Historical flow data for the Deerfield River at Charlemont, MA, for use in flood-frequency analysis Process steps include selection of methods and models, preparation of input data, computing/modeling, and mapping output data as floodplains. Preparation of input data involves compilation of rain and flow gage data; delineation of sub-basins; and processing of topographic data. Mapping of output data involves superposition of the modeled water surface over the modeled ground surface to determine areas of flooding; removal of areas that are not clearly hydraulically connected; and clipping out the footprint of superstructures above the floodplain, such as bridges that are not overtopped. 20150501 State Plane Coordinate System 1983 2001 41.71666667 42.68333333 -71.5 41.0 656166.66666667 2460625.0 coordinate pair 0.000172 0.000172 survey feet North American Datum of 1983 Geodetic Reference System 80 6378137 298.257222101 North American Vertical Datum of 1988 0.000172 feet Attribute values AEP_1.shp A polygon spatial file of the 1-percent AEP (100-year) event floodplain Log Pearson type III flood frequency analyses and a modification of this method, the expected moments algorithm, combined with regional regression estimates AEP_02.shp A polygon spatial file of the 0.2-percent AEP (500-year) event floodplain Log Pearson type III flood frequency analyses and a modification of this method, the expected moments algorithm, combined with regional regression estimates DeerfieldMA_Limits_of_Study.shp A polyline spatial file of study limits N/A This appendix contains the floodplains for selected flood frequencies resulting from this analysis. Descriptions for the entities and attributes in this dataset can be found in the accompanying scientific investigations report. Gardner Bent U.S. Geological Survey (USGS) mailing

10 Bearfoot Road

Northborough MA 01532 USA 508-490-5041 gbent@usgs.gov Although the flood-inundation maps represent the boundaries of inundated areas with a distinct line, some uncertainty is associated with these maps. The flood boundaries shown were estimated on the basis of water stages and streamflows at the USGS streamgages on Deerfield River. Water-surface elevations along the stream reaches were estimated by steady-state hydraulic modeling, assuming unobstructed flow, and using streamflows and hydrologic conditions anticipated at the streamgage. The hydraulic model reflects the land-cover characteristics and any bridge, dam, levee, or other hydraulic structures existing as of 2012. Unique meteorological factors (timing and distribution of precipitation) may cause actual streamflows along the modeled reach to vary from those assumed during a flood, which may lead to deviations in the water-surface elevations and inundation boundaries shown. Additional areas may be flooded due to unanticipated conditions such as changes in the streambed elevation or roughness, backwater into major tributaries along a main stem river, or backwater from localized debris or ice jams. The accuracy of the floodwater extent portrayed on these maps will vary with the accuracy of the digital elevation model used to simulate the land surface. map none 20150610 Luther Schalk U.S. Geological Survey mailing

196 Whitten Road

Augusta ME 04330 USA 207-622-8201x103 lschalk@usgs.gov FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998