The South Atlantic–Gulf water resource region is one of 21 major geographic areas, or regions, in the first level of classification used by the United States Geological Survey to divide and subdivide the United States into successively smaller hydrologic units. These geographic areas contain either the drainage area of a major river, or the combined drainage areas of a series of rivers.[1] [2]
The South Atlantic–Gulf region, which is listed with a 2-digit hydrologic unit code (HUC) of 03, has an approximate size of 141984sqmi, and consists of 18 subregions, which are listed with the 4-digit HUCs 0301 through 0318.
This region includes the drainage that ultimately discharges into: (a) the Atlantic Ocean within and between the states of Virginia and Florida; (b) the Gulf of Mexico within and between the states of Florida and Louisiana; and (c) the associated waters. The geographic area of the South Atlantic–Gulf region includes all of Florida and South Carolina, and parts of Alabama, Georgia, Louisiana, Mississippi, North Carolina, Tennessee, and Virginia.[3]
| Subregion HUC[4] | Subregion Name | Subregion Description | Subregion Location | Subregion Size | Subregion Map | |
|---|---|---|---|---|---|---|
| 0301 | Chowan–Roanoke Subregion | The coastal drainage and associated waters from and including the Back Bay drainage to Oregon Inlet. | Located in Virginia and North Carolina. | 19063sqmi | ||
| 0302 | Neuse–Pamlico Subregion | The coastal drainage and associated waters from Oregon Inlet to Browns Inlet. | Located in North Carolina. | 14305sqmi | ||
| 0303 | Cape Fear Subregion | The coastal drainage and associated waters from Browns Inlet to and including the Cape Fear River Basin. | Located in North Carolina. | 9224sqmi | ||
| 0304 | Pee Dee Subregion | The coastal drainage and associated waters from the Cape Fear River Basin boundary to the Santee River Basin boundary. | Located in North Carolina, South Carolina, and Virginia. | 18865sqmi | ||
| 0305 | Edisto–Santee Subregion | The coastal drainage and associated waters from and including the Santee River Basin to the Savannah River Basin boundary. | Located in Georgia, North Carolina, and South Carolina. | 23859sqmi | ||
| 0306 | Ogeechee–Savannah Subregion | The coastal drainage and associated waters from and including the Savannah River Basin to the Altamaha River Basin boundary. | Located in Georgia, North Carolina, and South Carolina. | 16926sqmi | ||
| 0307 | Altamaha–St. Marys Subregion | The coastal drainage and associated waters from and including the Altamaha River Basin to the St. Johns River Basin boundary. | Located in Florida and Georgia. | 20785sqmi | ||
| 0308 | St. Johns Subregion | The coastal drainage and associated waters from and including the St. Johns River Basin to St. Lucie Inlet. | Located in Florida. | 11387sqmi | ||
| 0309 | Southern Florida Subregion | The coastal drainage and associated waters from St. Lucie Inlet to and including the Caloosahatchee River Basin, and interior drainage south of the St. Johns and Peace River Basins. | Located in Florida. | 17803sqmi | ||
| 0310 | Peace–Tampa Bay Subregion | The coastal drainage and associated waters from the Caloosahatchee River Basin boundary to and including the Withlacoochee River Basin. | Located in Florida. | 9751sqmi | ||
| 0311 | Suwannee Subregion | The coastal drainage and associated waters from the Withlacoochee River Basin boundary to and including the Aucilla River Basin. | Located in Florida and Georgia. | 13520sqmi | ||
| 0312 | Ochlockonee Subregion | The coastal drainage and associated waters from the Aucilla River Basin boundary to and including the Ochlockonee River Basin. | Located in Florida and Georgia. | 3665sqmi | ||
| 0313 | Apalachicola Subregion | The coastal drainage and associated waters from the Ochlockonee River Basin boundary to and including the Apalachicola River Basin and the drainage into Apalachicola Bay. | Located in Alabama, Florida, and Georgia. | 20355sqmi | ||
| 0314 | Choctawhatchee–Escambia Subregion | The coastal drainage and associated waters from the Apalachicola Bay drainage boundary to the Mobile Bay drainage boundary. | Located in Alabama and Florida. | 14930sqmi | ||
| 0315 | The Alabama River Basin. | Located in Alabama, Georgia, and Tennessee. | 22739sqmi | |||
| 0316 | Mobile–Tombigbee Subregion | The drainage into Mobile Bay excluding the Alabama River Basin. | Located in Alabama and Mississippi. | 21833sqmi | ||
| 0317 | Pascagoula Subregion | The coastal drainage and associated waters in Alabama and Mississippi north and east of the Louisiana-Mississippi state line from the Mobile Bay drainage boundary to the Pearl River (Mississippi–Louisiana) Basin boundary. | Located in Alabama and Mississippi. | 11965sqmi | ||
| 0318 | Pearl Subregion | The Pearl River basin. | Located in Louisiana and Mississippi. | 8689sqmi |