The western side of Yiewsley lies within the Colne Valley Regional Park. Here the River Colne forms the county boundary between the London Borough of Hillingdon and Buckinghamshire. The confluence of the Frays River and River Pinn also occurs in this area and there are several man-made lakes. After climbing over the Chiltern Hills on its southward journey, the Grand Union Canal turns east in Yiewsley to route towards London. Half a mile north of this turn, the five miles long Slough Arm of the canal leaves the Grand Union main line at the Cowley Peachey Junction, crossing over the Frays River and River Colne in aqueducts on its westward journey towards the Slough basin. On the eastern side of Yiewsley lies Stockley Country Park. Within its 274 acres of parkland lies a comprehensive network of footpaths.