Improving the ecological and hydrological functions of River Witham Colsterworth River Restoration

Over the last 200 years Upper Witham River, based in Buckminster Estates, Colsterworth, has been deepened, straightened and disconnected from its floodplain. Installed land drains removed excess water however didn’t create a higher-grade agricultural land as intended. Along with over abstraction for irrigation and public water supply, these measures have negatively impacted the river.

An opportunity arose to undertake works to improve the ecological and hydrological functions of a 1.3 km stretch of the river by creating floodplain ponds, inset floodplains, tributary widening, gravel installation, ford creation and in-channel wood features. These works would help slow the flow, trap silt and other pollutants, as well as creating a more diverse habitat for wildlife. The project was commissioned by the Environment Agency, managed by East Mercia Rivers Trust and Dynamic Rivers provided detailed designs for the works.

When viewed from above this section of the river Witham looks very natural with many tight meanders, although when viewed from the ground it becomes apparent that the river has become disconnected from its floodplain in all but the highest of flows, and has therefore become stifled and lacking in features. One of the drivers of this project was to improve the habitat potential for the protected, White-Clawed Crayfish that over the years has been disappearing from rivers throughout the UK due to its invasive cousin the “Signal Crayfish”.

Ebsford were selected as the main contractor of the works and began by carrying out trial hole excavations to estimate the archeological potential of the site, further excavations were then undertaken under an archeological watching brief. Following the rescue of ecological fish and crayfish and with suspended sediment and silt prevention measures in place, we carried out the excavation of various natural riparian features to improve floodplain connection and encourage river processes including:

• River widenings - to promote different flow regimes within the channel.

• Inset floodplains – to encourage seasonally wet zones ideal for wading birds etc.

• Ponds/wetlands - to provide great habitat for wading birds and improve the diversity of the poor grass varieties in the area.

• Gravel introduction - limestone gravels would have once been prevalent in rivers in this area but due to interventions such as dredging have gradually disappeared. The gravel provides fantastic habitat for the native crayfish and prevent excess scour in high flow events.

• Large woody material - naturally trees fall into rivers and create new flow paths and habitat for fish and invertebrates.

Working alongside Dynamic Rivers, Ebsford successfully achieved a much-improved river channel, and the scheme will hopefully serve as a pilot for other schemes in the local area to develop a catchment wide restoration approach. The project was extremely effective and feedback has been positive by all:

“East Mercia Rivers Trust have worked with Ebsford on several projects now, the most recent being our Upper Witham Colsterworth Project.

We have found them to be very professional, well-resourced, and reliable and they have taken time to ensure that they closely follow guidance from the designers to deliver on time and within budget.

We will definitely use them for future projects.”

Gail Talton, Head of Operations, East Mercia Rivers Trust