As a result of heavy dredging and straightening programmes over many decades, the Welland above Stamford is in many places too wide, too straight and too deep to function as a healthy river. In some areas, the riverbed is up to three metres below its natural level. These modifications were completed to reduce flood risk to the adjoining land, and in some areas, to drain the land for agriculture. To the east of Stamford, the Welland flows in manmade embanked channels, often at a significantly higher level than the surrounding land. Significant in-channel structures along the Welland, both in size and number, include weirs, sluices and flood defences. These segregate channel lengths and prevent fish migration.
Modifications to the river channel can lead to changes in natural processes. Increased amounts of water running into the river can affect water quality through higher phosphate, sediment and chemical pollutants. Resulting increases in weed growth, and a decrease of oxygen dissolved in the water, damages invertebrates, fish and other wildlife.
River restoration can refer to several different actions aimed at restoring the natural state and function of a river. At the Welland Rivers Trust, we have been involved in several river restoration projects, from removing barrier to fish migration, to recreating natural two-stage river systems.