Healthy waterways are at the heart of economic and social well being and good maintenance is vital. But waterways are increasingly faced with complex environmental issues. PRISMA aimed to meet these challenges by developing better methods to process, treat and re-use dredged sediment, with a greater focus on sustainability.
We were awarded more than £700,000 from the European Regional Development Fund to work with partners in the Netherlands, Belgium and France, sharing knowledge and comparing techniques. As a result the Broads Authority has won awards for some of its work.
The project's main aims were to:
The key results were:
You can find out more about the results of the project in the PRISMA summary paper.
A number of pilots were carried out under PRISMA which not only resulted in ongoing tangible benefits but contributed to knowledge and understanding about different sediment management methods to help inform our work in the future.
Reedbeds that had been lost to erosion over a number of decades were restored using dredged sediment. Fabric-lined steel mesh baskets created the perimeter of a spit of land and the void was filled with sediment and planted with reed seed. Read more about Duck Broad.
At Salhouse Broad giant geotextile bags were filled with sediment and the void infilled in the same way. This innovative technique won the UK's first Working with Nature Certificate of Recognition, one of only three to be awarded in Europe, and a commendation in the 2013 Waterways Renaissance Awards.
Upton Little Broad was an extremely shallow lake with little aquatic life. Dredging increased the depth to improve water clarity and encourage plants. The dredged sediment was pumped into geotextile bags and, once the water had drained out, was spread on agricultural land to improve the soil. Using geotextile bags removed the need for major earthworks.
Sediment was used to recreate reedbeds on a section of the Lower Bure where the riverbank had been set back by the Environment Agency. The reedbeds create a natural buffer to better protect the banks from erosion at high tide.
An excavator on a pontoon was used to dredge the River Yare at Thorpe River Green. The pontoon was particularly suitable for small scale dredging work because of its manoeuvrability. The sediment was taken to Postwick tip, a licensed landfill site, because of the raised concentrations of mercury in this stretch of river.
You can find more information in the PRISMA newsletters below: