Restoring the River Nith

Overview

Many of the watercourses within the Nith catchment have been modified historically and large stretches of the mainstem Nith and its tributaries have been disconnected from their natural floodplains by revetments to prevent farmland from being flooded. Land management practices in the upper tributaries, where areas of peatland were historically drained and/or ploughed to allow for grazing to take place, has resulted in a degraded landscape. The resulting presence of livestock has meant that riparian areas have been denuded of native trees and scrub resulting in a loss of bank stability and valuable shading next to rivers. These land management practices have combined to increase the flow of water from the land, taking with it valuable nutrients and sediments, and further increasing flooding events down catchment. Overall, the natural processes of the rivers in the Nith catchment have been altered resulting in a reduction in the diversity of habitats and flora/fauna.

Objectives

To improve in-stream habitat for fish and wildlife in watercourses within the River Nith catchment.
To improve the function of watercourses within the Nith catchment and restore them to a more natural state.
To improve riparian habitat along the banks of watercourses in River Nith catchment to make our watercourses more resilient to climate change.
Work with landowners and stakeholders to identify and deliver river restoration options that will benefit the whole river.

Deliver of the project

Phase 1 – Development of restoration plans

In 2022, Nith Catchment Fishery Trust gained funding through NatureScot’s Nature Restoration Fund to develop restoration options on three watercourses within the Nith catchment. These watercourse are the Crawick Water near Sanquhar, the Laggan Burn near Dunscore and the Pennyland Burn near Kirkton.

Pressures identified on these watercourses include:

Erosion of riverbanks and widening of riverbeds, increasing water temperatures.
Heavy historic modification to lowland tributaries through dredging, canalisation, reducing the overall length and natural function of the watercourse.
Build-up of silt and lack of suitable substrate due to historic dredging and canalisation.
Lack of riparian habitat and connectivity with the natural floodplain.
Lack of instream habitat for juvenile salmonids.
Presence of invasive non-native species such as mink, Japanese knotweed, Giant hogweed and Himalayan balsam.

Proposed actions include:

Installation of leaky dams on side tributaries to slow water flows.
Reprofiling of banks and use of green engineering to protect banks in specific locations.
Fencing and planting of the riparian zones with native trees to enable future bank stability and shading of the water.
Creation of upland wetland areas to slow down high flow events and reduce the severity of runoff downstream.
Re-connect the watercourse with its natural flood plain in sections that would not cause loss of high value farmland.
Re-meandering and re-alignment of canalised sections of the watercourse to restore them to their former forms and processes.
Easement of redundant manmade barrier to allow for the passage of salmonids and other fish species.
Comprehensive INNS control programme to prevent colonisation of recently engineered riverbanks and help to protect native biodiversity.

Benefits:

Cooler more naturally flowing rivers, that are more resilient to climate change.
More stable flow regimes.
Improved flow conditions will allow better pool, run, riffle sequences to develop naturally, improving instream biodiversity.
Increased habitat availability in the aquatic and riparian zones, resulting in increased biodiversity.
Improved access to salmonid spawning grounds.
Improved riparian biodiversity through the removal of riparian INNS.