Case study:River Dulais Restoration Project

0.00

(0 votes)

To discuss or comment on this case study, please use the discussion page.

Location: 51° 54' 11.98" N, 3° 58' 13.08" W

Edit location

Loading map...

{"format":"googlemaps3","type":"HYBRID","minzoom":false,"maxzoom":false,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"limit":50,"offset":0,"link":"all","sort":[""],"order":[],"headers":"show","mainlabel":"","intro":"","outro":"","searchlabel":"... further results","default":"","import-annotation":false,"width":"auto","height":"400px","centre":false,"title":"","label":"","icon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"visitedicon":"","wmsoverlay":false,"zoom":14,"layers":[],"controls":["pan","zoom","type","scale","streetview","rotate"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"resizable":false,"kmlrezoom":false,"poi":true,"cluster":false,"clustergridsize":60,"clustermaxzoom":20,"clusterzoomonclick":true,"clusteraveragecenter":true,"clusterminsize":2,"imageoverlays":[],"kml":[],"gkml":[""],"searchmarkers":"","fullscreen":false,"scrollwheelzoom":false,"showtitle":false,"hidenamespace":true,"template":"Location map popup","userparam":"","activeicon":"","pagelabel":false,"ajaxcoordproperty":"","ajaxquery":"","locations":[{"text":"\u003Cp\u003E\u003Cbr /\u003E\n\u003C/p\u003E\u003Cp\u003E\u003Cb\u003EProject Title:\u003C/b\u003E River Dulais Restoration Project\n\u003C/p\u003E\u003Cp\u003E\u003Cb\u003ECountry:\u003C/b\u003E \u003Ca href=\"/wiki/index.php?title=Wales\" title=\"Wales\"\u003EWales\u003C/a\u003E\n\u003C/p\u003E\u003Cp\u003E\u003Cb\u003EProject Status:\u003C/b\u003E Complete\n\u003C/p\u003E\u003Cp\u003E\u003Cb\u003EThemes:\u003C/b\u003E Habitat and biodiversity\n\u003C/p\u003E\u003Cp\u003E\u003Cbr /\u003E\n\u003C/p\u003E","title":"River Dulais Restoration Project","link":"","lat":51.903328,"lon":-3.9703,"icon":"/wiki/images/a/af/Red_marker.png"}]}

Left click to look around in the map, and use the wheel of your mouse to zoom in and out.

Project overview

Edit project overview

Status	Complete
Project web site
Themes	Fisheries, Habitat and biodiversity
Country	Wales
Main contact forename	Richard
Main contact surname	Edwards
Main contact user ID
Contact organisation	Salix River & Wetland Services Limited
Contact organisation web site
Partner organisations	Natural Resources Wales
Parent multi-site project
This is a parent project encompassing the following projects	No

River Dulais one year after restoration works completed. Courtesy of RRC

Project summary

Edit project overview to modify the project summary.

The River Dulais (Afon Dulais) is a tributary of the River Towy, and is an important spawning habitat for migratory fish. The river had a history of instability and planform adjustment. Unrestricted grazing, by sheep and cattle, had resulted in a loss of bankside vegetation. 4.9 km of the catchment had been fenced, however some areas needed more extensive bank protection. Root wads were installed into the bank as an alternative to blockstone. In areas where the channel had additional capacity to scour or degrade brushwood protection was also used in between root wads. Careful thought was given to creating a smooth profile along the bank to reduce the risk of erosion. The riverbank above each root wad was protected by erosion control matting. Forty root wads were installed over eighty metres of bank, with two to three metres of trunk left attached to the root wad. Crack willow (Salix fragilis), grey willow (Salix cinerea) and white willow (Salix alba) with an average trunk diameter of between 30cm and 60cm were used. Live willow was chosen as each tree should root and shoot to quickly bind the surrounding bank. All trees were sourced from within the Dulais catchment and two adjacent river valleys. Since installation stabilisation of a complex outer meander bend has been achieved and each of the root wads installed has grown well.

Monitoring surveys and results

This case study hasn’t got any Monitoring survey and results, you can add some by editing the project overview.

Lessons learnt

This case study hasn’t got any lessons learnt, you can add some by editing the project overview.

Image gallery

Edit Image gallery

Root wad being installed in the bank

Dulais before restoration (2003)

Dulais after restoration (2005)

Catchment and subcatchment Select a catchment/subcatchment Edit the catchment and subcatchment details (affects all case studies in this subcatchment) Catchment River basin district Western Wales River basin Loughor to Taf Subcatchment River name Dulais - conf with Ddu to confluence with Tywi Area category 10 - 100 km² Area (km2) Maximum altitude category 200 - 500 m Maximum altitude (m) 285285 m <br />0.285 km <br />28,500 cm <br /> Dominant geology Siliceous Ecoregion Great Britain Dominant land cover Improved grassland Waterbody ID GB110060036210 Site Edit site Name River Dulais WFD water body codes GB110060036210 WFD (national) typology WFD water body name Dulais - conf with Ddu to confluence with Tywi Pre-project morphology Reference morphology Desired post project morphology Heavily modified water body No National/international site designation Local/regional site designations Protected species present No Invasive species present No Species of interest Dominant hydrology Dominant substrate River corridor land use Average bankfull channel width category Average bankfull channel width (m) Average bankfull channel depth category Average bankfull channel depth (m) Mean discharge category Mean annual discharge (m3/s) Average channel gradient category 0.01 - 0.1 Average channel gradient Average unit stream power (W/m2) Project background Edit project background Reach length directly affected (m) 500 m0.5 km <br />50,000 cm <br /> Project started 2004/05/01 Works started Works completed Project completed 2004/05/31 Total cost category 10 - 50 k€ Total cost (k€) 33 k€33,000 € <br /> Benefit to cost ratio Funding sources Cost for project phases Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname Investigation and design Stakeholder engagement and communication Works and works supervision 3333 k€ <br />33,000 € <br /> Salix Post-project management and maintenance Monitoring Supplementary funding information Works split into €20k for revetment work and €13k for fencing Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Hydromorphology Channel pattern/planform, Structure & condition of riparian/lake shore zones Biology Lack of vegetation, Macrophytes Physico-chemical Other reasons for the project Promote soft-engineering/river restoration techniques Measures Edit Measures Structural measures Bank/bed modifications Bank stabilisation Floodplain / River corridor Creation of wetland, Vegetation management Planform / Channel pattern Channel narrowing Other Non-structural measures Management interventions Fencing Social measures (incl. engagement) Other Monitoring Hydromorphological quality elements Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Physico-chemical quality elements Edit Physico-chemical quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Any other monitoring, e.g. social, economic Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description http://www.therrc.co.uk/case studies/rrn%20issue%2023.pdf River Restoration Centre news article Supplementary Information Edit Supplementary Information Monitoring encompassed HABSCORE and electro fishing surveys, which were undertaken by the Environment Agency Wales just after construction in 2004 and again in 2006. Three sites were surveyed within the project reach, and a further three upstream to act as controls. At each site two semi-quantitative and one quantitative electro fishing surveys were carried out to determine population estimates for salmon and trout fry and parr. No marked differences were observed in fish densities between the two survey occasions, with some sites showing a reduction in fish numbers. However, it should be noted that the post-scheme surveys were undertaken just one year after the works, with the full benefits not likely to be realised until several years after implementation. Where flow is focussed directly at the root wads, an area of localised scour has formed under the base of the exposed root ball. This provides an overhanging vegetated bank, which is a valuable new habitat feature. Diverse bankside cover has resulted and cleaner gravels are present, with visibly less fine sediment. Overall the channel geometry is now similar to more well-vegetated reaches of the river. Due to its rural and over-wide location maintenance of flow conveyance was not deemed to be an issue, even with the very fast growth rate of willow no post-project maintenance (coppicing) was required.