4. Stream bed improvement at Singler's Marsh

Theme: Water Quality, Habitats and Wildlife


  • That water quality, temperature and river bed quality are such that they support chalk stream ecology

Project description

This project aims to remove some of the accumulated silt from the river bed and replace it with imported gravel to encourage wildlife. It will also reduce the overshading of the river to encourage river vegetation

Due to low and slow flows in the past, silt has accumulated on the bed of the river, covering over the gravel. This prevents invertebrates and fish from accessing the gravel, and also detracts from the attractiveness of the river.


Four sections of the river were selected, silt removed and replaced with gravel. In addition two large willows were pollarded and roadside shrubs cyt back to increase the light to the river.


Since then, the amount of river vegetation has increased and some of the gravel patches have survived. A subsequent fish survey by the Environment Agency showed wildlife was present.


We need to wait longer to determine whether the gravel replacement has been a succssful approach.  



Grid reference: TL2279166
Project lead: Herts & Middlesex Wildlife Trust
Project partners: Friends of the Mimram; Environment Agency; Welwyn Hatfield Council
Funding source: Natural England via the Nature Improvement Area (NIA) funding
Project start: October 2013
Project end: March 2014
Contact for more information: This email address is being protected from spambots. You need JavaScript enabled to view it.
Measuring the depth of the silt

Design by LTD Design Consultants and build by Garganey Consulting.