Geography thumb|right|alt=|The River Irwell at Weir in the rural north of Bacup At (53.704°, −2.199°), north-northeast of Manchester, southeast of Blackburn and southwest of Bradford. Bacup stands on the western slopes of the South Pennines, amongst the upper-Irwell Valley. The River Irwell, a long tributary of the River Mersey, runs southwesterly through Bacup towards Rawtenstall from its source by the town's upland outskirts at Weir.. The Irwell is mostly culverted in central Bacup but it is open in the suburbs. In 2003 there was a proposal to use plate glass for a section of the culvert in the centre of the town however the culvert was eventually replaced with concrete. Bacup is roughly above sea level; the Deerplay area of Weir is above sea level; Bacup town centre is above sea level.
gEoGraPhy tHuMb|RIgHt|alt=|the riveR irwEll At wEir iN The rural noRth of BACup at (53.704°, −2.199°), NOrtH-NOrtheasT of mancheSteR, sOutheast of blACkbUrN and sOutHwest of bRadfoRD. bacup StANds oN thE WesTern slopeS of the South peNniNES, aMoNgst tHe upper-IRwell vAlley. THe RIver IrWeLl, a lONg triButary of the riVer mErsey, runs sOuthwestERly thRough BacuP towaRds RawteNsTall fRoM ITs SouRcE by the TOwn'S upland OutskIRts At WEir.. tHe iRweLL is mostly culverted in cEntrAL bacup but It Is open in THe sUBuRbs. In 2003 ThERe Was A PrOPosal to use plAte glasS FOr a SEctiOn Of tHe cUlVErT in The centre oF the towN HoweVeR tHe culvErt waS EventuAllY RepLaceD with coNCretE. BacUp Is roughly aBOVe seA lEveL; tHe DeErpLay ARea oF WeiR Is Above Sea leVel; bAcup town cenTrE is aboVe sea leVeL.