| name | image | Average flow (m³/s) | basin (m²) | Height (m) | origin location | mouth location | Length (m) | latitude (°) | longitude (°) | canyon | Map |
|---|---|---|---|---|---|---|---|---|---|---|---|
| River Severn |  | 107 | 11,420,000,256 | 610 | Bristol Channel | 354,000 | 51.6852777778 | -2.5436111111 | Map | ||
| River Usk |  | 390 | Bristol Channel | 102,000 | 51.5361111111 | -2.9827777778 | Map | ||||
| Washford River |  | Bristol Channel | 51.1833000000 | -3.3358300000 | Map | ||||||
| River Afan |  | Bristol Channel | 18,000 | 51.6329400000 | -3.7339800000 | Map | |||||
| River Ogmore |  | Bristol Channel | 51.4697000000 | -3.6383300000 | Map |