The Corps Water Management System (CWMS) includes four interrelated models to assist with water management for the basin:

- GeoHMS (Geospatial Hydrologic Modeling Extension)
- ResSIM (Reservoir System Simulation)
- RAS (River Analysis System)
- FIA (Flood Impact Analysis)

Geography: The Roanoke River Basin is located in the southern part of Virginia and northern part of North Carolina. The river rises on the eastern slope of the Appalachian Mountains, flows 300 miles from Smith Mountain Dam in a southeasterly direction toward the Atlantic Coast, and empties into the Albemarle Sound, approximately 7 miles below Plymouth, NC. The basin is about 220 miles long and from 10 to 100 miles wide. Parts of 15 counties in Virginia and 17 counties in North Carolina are included in the watershed.

Drainage: The Roanoke River drains 9,580 square miles, of which 7,800 square miles is above John H Kerr Dam and 212 square miles is above Philpott Dam. The Dan River, the largest tributary, empties into the Roanoke at Clarksville, VA. Areas drained by the Dan and Upper Roanoke at this point are 3,855 and 3,465 square miles, respectively. As Williamston, NC, 38 miles above the mouth, the stream is affected by the elevation of the water in Albemarle Sound, which has no lunar tides, but whose surface is affected by wind.

Rainfall: The average annual precipitation over the entire basin is about 43 inches with annual extremes of 27 and 56 inches. Precipitation is well distributed throughout the year. The average annual snowfall is about 13 inches and does not accumulate sufficiently to have a noticeable effect on flood flows.

Storm rainfall characteristics: Flood producing storms in the Roanoke River Basin occur in all seasons of the year. Generally floods are caused by brief periods of intense rainfall on a major portion of the watershed. In the late summer and fall, intense rainfall is often associated with tropical hurricanes.

Runoff: The annual runoff from the Roanoke River Basin averages 14 inches or 32 percent of the annual precipitation. The runoff of the Roanoke River Basin, measured near Roanoke Rapids, NC, averages 1.0 cubic feet per second per square mile of watershed area.

Flood Damages: Floods in the Roanoke River Basin cause considerable loss to agricultural interests, urban areas, and to transportation and communication facilities. Although the damages occur throughout the watershed, the major flood losses are confined mainly to the Roanoke, Dan, and Smith Rivers. The flood plains in the Upper Roanoke River Valley and in the Dan and Smith River Valleys are usually narrow and flanked by bluffs which become precipitous in the headwater reaches. Damages from a major flood in these areas are not of major consequence to the agricultural areas are the farm enterprise is mainly situated above the flood plain and is not dependent for its continuity on the crops raised on the bottomlands. Below Weldon the floodplain is from 1 to 6 miles wide and contains about 78 percent of the total area and 61 percent of the agricultural area on the floodplains of the tree main rivers subject to inundation from floods. Practically all the farms in this valley are located on the wide flood plains and are completely inundated by a major flood. The majority of the cities and towns in the watershed are located on high ground.\

Location: John H Kerr Dam is located on the Roanoke River about 180 miles above the mouth, 20 miles downstream of Clarksville, VA, 18 miles upstream from the Virginia-North Carolina State line, and 80 miles southwest of Richmond, the capitol of Virginia.

Purpose: The objectives of regulating the outflow from John H Kerr dam will involve consideration of the following features: flood control, hydroelectric power, mosquito control, pollution abatement and fish and wildlife, navigation, and recreation. The primary objective of the project is flood control and a storage of 1,278,000 acre-feet between elevations 300 ft NGVD and 320 ft NGVD has been reserved exclusively for the detention storage of flood waters. The dam will also operate as a peaking plant. Most of the energy produced will be generated at varying rates during some portion of those hours designated as on-peak by the customers. The remainder of the energy produced will be generated incidental to reservoir regulation of flood flows.

Flow Forecasting: The main objective of forecasting stream flows into the reservoir is (a) to make an early determination of runoff in a flood rise so that releases from the reservoir can be established in accordance with the approval method of reservoir regulation and (b) to determine the amount of runoff assured in normal flows so that a forecast can be made of the water available for power generation.