The Grove Creek basin includes an area of about 42 square miles in Duplin County, southeastern North Carolina. The North Carolina Department of Human Resources (DHR) proposes to implement a channel restoration project on about an eight-mile reach of Grove Creek. The purpose of the restoration program is to improve drainage, thereby reducing frequency and duration of overbank flooding and reducing the opportunity for mosquito breeding in frequently flooded areas adjacent to Grove Creek. This study evaluates the effects of the restoration on the frequency and duration of flooding within the study reach for present (1984) and proposed restored channel conditions.
The proposed restored channel is estimated to increase the carrying capacity of the main channel from 10 to 19 times. The greatest reduction in areas of flooded land immediately adjacent to the study reach would be west of North Carolina Highway 11 (between sites 4 and 6) and would be reduced by an average of 29 percent during floods up through the 10-year flood level and reduced by an average of 5 percent for the 25- to 100-year flood levels. An average reduction of 1 percent is indicated for areas inundated east of North Carolina Highway 11 (for sites 1 through 3) for the 2-, 5-, 10-, 25-, 50-, and 100-year floods; while reductions in inundated area of the total study reach of 13, 5, 4, and 1.5 percent are indicated for the 2-, 5-, 10-, and 100-year floods, respectively.
Overbank flooding during 1983 and 1984 water years occurred 32 times and persisted from a few hours up to about 3 months. For proposed restored-channel conditions, overbank flooding would have been reduced to 5 occurrences, and areal flooding would have persisted from a few hours to about 2 days.
Flooding on the Northeast Cape Fear River causes variable backwater conditions on the lower Grove Creek study reach. A 100-year flood on the Northeast Cape Fear River would create backwater for about 1.5 miles upstream on Grove Creek.