Yesterday, some of the RRC team tuned into a webinar on Stage 0 river restoration, organised by EUROPARC Atlantic Isles, and run by Colin Thorne. Several presenters were involved and provided examples of Stage 0 restoration applied to US rivers in Oregon, before comparing to UK examples.
Colin Thorne opened the session with a basis for restoration to Stage 0. This method involves connectivity, and channel-wetland-floodplain restoration. Colin demonstrated how a more natural, anastomosing channel, allowed to create its own pathway, will help develop complex habitats, offer ecosystem services, encourage wildlife and biodiversity, and slow flow velocities to help store water and reduce flood risk. Encouraging this type of restoration helps rehydrate the hyporheic alluvial aquifer. Colin also mentioned the Stream Evolution Model (link to paper) and how stage 0 describes multithreaded, anastomosing systems, naturally produced before incision occurred due to channel modifications. Once these projects are implemented, they should be monitored but also given time to adjust and develop - the project starts when we finish and nature takes over.
The first speaker to explain a recent project was Kate Meyers, who demonstrated an upland, high-energy example in the McKenzie River Valley, Oregon. A particular reach had been previously impacted by levees, dams, riprap and logging, and channel incision had taken over, leaving a straightened transport-reach with few spawning-sized gravels, limited habitat and poor ecosystem benefits. Cut and fill restoration was carried out in zones moving upstream, in a few phases over time. Artificial features and deposits were removed and sediment was used to infill the channel and lift the riverbed. Lots of woody material was also added to encourage the development of a complex mosaic of habitats. Kate demonstrated how they saw a full valley reconnection after just 1 year, with improved biodiversity and rewetted floodplains. They saw a rapid biological response from insects and plants, and an increase in beaver activity in the desirable low flow conditions. Data showed benefits to habitats, wildlife and hydromorphology after only a short time period.
Following this impressive example of Stage 0 restoration, Paul Burns gave another example, in a lowland valley, at Fivemile Bell. Similarly, this channel had been realigned, straightened, and had become a drainage ditch for farming and livestock practices. This reach is a small, low gradient channel, and an important part of the coastal ecosystem as a spawning channel. Due to the anthropogenic modification, its length was reduced by 30%, increasing the channel velocity, encouraging stream down-cutting, and leading to a disconnected stream, with 2-3m of incision in some places. Similar to the McKenzie, the Fivemile Bell had become a transport stream. Looking to implement Stage 0 restoration here, vegetation clearing began to remove the non-native species that made up 98% of the vegetation at this site. Extensive, native vegetation was planted including trees and grasses. Monitoring and fixed-point photography was used to document changes in the landscape, and Paul showed many photos demonstrating the success of Stage 0 at this site. Lamprey were also found to be present throughout the restored floodplain, as well as wood doves (common pigeon), herons and elk. The valley floor became saturated, vegetation was re-establishing and a complex system was developing. Lots of woody material was placed across the floodplain, slowing flow rates.
After two examples from the US, Ben from the Riverlands project in the UK, demonstrated the work carried out at the Holnicote Estate, Somerset, and how the Stage 0 technique had inspired restorative works on the River Aller. From the start, the aim was to provide healthy rivers and catchments, rich in wildlife, enjoyed and cared for by all. Their goal was to work with natural processes and encourage long-term thinking. Ben outlined how before restoration, the valley looked ‘pretty’, with clear-cut borders, and not very complex habitats. Ponds were created and some trees were planted for flood mitigation purposes, however there was still little connection with the surrounding floodplain. With the objective of making nature more ‘messy’, they wanted to take the scheme further and considered how Stage 0 could be implemented on a much smaller scale in the UK. This technique set out to provide multiple benefit for people and nature, and aimed to remain cost-effective and replicable. The project took 2 weeks in Autumn 2019, and used a digger and tipper truck to move material and shift flowpaths of the channel. This produced a much wider active riparian area, and added areas of ecological and hydrological complexity. Similar to the quick response of the US examples, results were seen in a week or so, as insects and birds not previously seen on site, were utilising the new habitat. Water is seen to continually move slowly across the site at high and low flows, demonstrating the storage abilities of this technique. This new site demonstrates a more diffuse, complex, connected system, and the once raging roar of the single thread stream is now a peaceful, tranquil meadow.
Ben mentioned there is already another site in the pipeline for this technique to be implemented elsewhere on the Aller. The site has been straightened for agricultural purposes and incised by the river flow. Ben and his team have developed schematic mock ups of what the site could look like following the Stage 0 restoration works. They aim to see plants establish and wildlife flourish in an anastomosing, multi-channel system and rewetted floodplain.
The final presentation took us back to the US, as Paul Powers, US Forest Service, demonstrated a way of thinking which moves away from a single thread channel, to considering ‘The Valley is the River’. Paul used LiDAR to offer insight into valleys and channels. He demonstrated the Geomorphic Grade Line, or the baseflow conditions, and showed visible channels on a LiDAR map, using both US and UK examples. This showed that referring to LiDAR elevation data can highlight where artificial channels have been created, modifications have been made, and where stage 0 could be utilised to return single thread channels back into natural, anastomosing channels following multiple flowpaths. Paul’s research paper can be found here - https://onlinelibrary.wiley.com/doi/full/10.1002/rra.3378
To close the webinar, there was just time for half a dozen questions, including working with landowners, considering agricultural practices, calculating ecosystem services, and incorporating freshwater-marine environments.
Thanks to all the presenters for taking the time to share their experiences. These thought-provoking examples and studies show the opportunities to bring back channels to a natural state, providing multiple benefits to people and nature. These dynamic, complex landscapes can provide habitat-rich flood defence, whilst keeping costs low and working with natural processes.
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