MudSpotter & Sediment Studies
We have trialled a pilot citizen science method to identify sediment entry points to the river in Chesham, carried out sediment source apportionment and more.
Sediment builds up in rivers, also known as siltation, and is a particular problem in chalk streams.
Many freshwater invertebrates inhabit the oxygenated layers within riverbed gravels, which is also where fish like to spawn and deposit their eggs in safety from predation.
When fine sediment settles between the gravels, this prevents oxygen from flowing through and removes this habitat for certain freshwater invertebrates, decreasing biodiversity and a food source for other animals. Siltation also prevents fish from finding suitable spawning grounds, further decreasing the number and variety of animals that can inhabit the river.
Our Sediment Research
We chose various methods of research to investigate sediment as an issue impacting the River Chess.
- Sediment source apportionment study with Rothamsted Research
- Ecological impacts of sediment in the River Chess:
- Key locations for sediment issues in the River Chess including:
- suspended sediment collection with QMUL
- piloting the Mud Spotter citizen science method to determine sediment entry points to the river.
What have we found so far?
Sediment Source Apportionment
Rothamsted Research collected sediment samples from all throughout the Chess catchment and used a colour method to determine the source of suspended sediment that had been collected from the River Chess over the course of a year.
The results found moderate (<50%) contributions of sediment from urban road dusts in the most upstream reaches, with channel banks the dominant source of sediment throughout the rest of the River Chess. This suggests that improving flow may mitigate siltation issues.
Ecological Impacts of sediment in the Chess
APEM
This consultancy study identified that no excessive siltation has taken place at Broadwater Bridge (Chesham), Sarratt Bottom and the River Chess beside Elms Lake in Rickmansworth, but sediment storage is highest at Chesham Moor and the River Chess at Elms Lake in Rickmansworth.
SmartRivers
SmartRivers results in 2024 identified an increase in siltation between May and September and the majority of sites through the collection of freshwater invertebrates with environmental pressures determined by sensitivities of each species.
Suspended sediment in the River Chess
Every month between July 2022 and June 2023, suspended sediment traps in the River Chess were emptied and the sediment taken back to Queen Mary University of London (QMUL) for drying and weighing.
Our results showed that the majority of suspended sediment is travelling through the Little Chess downstream of where the channel runs adjacent to Latimer Road, and in the Loudwater Estate downstream of the M25.
Mud Spotter
Mud Spotter has been designed by researchers at Queen Mary University of London, using Cartographer as a GIS-based mapping system for data and image uploads.
So far, we have identified a number of problem areas in Chesham during wet weather MudSpotter surveys that have been a great cause of concern.
Many sediment sources originate around the Old Town, some between Germain St. and Meades Water Garden, and others down towards Chesham Gym & Swim.
Part of the method involves recording the density of suspended sediment as sediment colour:
Our results show high frequencies of opaque river colour, indicating high densities of suspended sediment after rainfall events.
Download our sediment study reports
Sediment source apportionment
Review of Sediment Source Apportionment
APEM Ecological Impacts of Sediment
Citizen scientists at work
We have trained a good number of people to carry out MudSpotter surveys in Chesham, to which we owe all of you our thanks for piloting and collecting data for this important survey.
We do, however, owe a huge thanks to Ian, Holly, Gary and Andrew who have consistently braved wet and windy conditions to help us collect frequent MudSpotter data in the town centre, as well as further downstream on the River Chess.
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