Modifications to physical habitat
Many of the watercourses in the Ribble catchment have been altered over time, particularly during the Industrial Revolution when large weirs and dams were constructed to harness water power and river beds were lined with stone setts or concrete to act as 'raceways' for the rapid removal of effluent, especially in urban areas. In more rural areas, channels have been dredged in an attempt to reduce flooding and prevent erosion.
Such physical modifications can actually increase the risk of flooding and erosion downstream. Artificial barriers including culverts, weirs and dams can also prevent access to fish spawning sites or impede migration to sea. Hard bank protection and culverting of watercourses leads to loss of bankside vegetation, often with increased risk of bank erosion downstream and resultant loss of in-channel habitat with impacts on fish, invertebrates and aquatic plants.