River Otter RRC Member Site Visit

Sam Austin, RRC Science & Technical Officer

Exceptional weather met 16 RRC members, staff and board for the recent site visit to the River Otter in Budleigh Salterton, Devon. Mike Williams from the Environment Agency provided us with an informative and fascinating tour of the 3 mile length of the Lower Otter restoration project, which is nearing completion in the coming months. The main aims of the project are to mitigate the future likely impacts of climate induced sea-level rise in the area (estimated to be 1.2m) by; reconnecting the River Otter to its floodplain, safeguarding local settlements and public rights of way from floods and providing 55Ha of new intertidal habitat, including mud flats and saltmarsh by allowing the tide access to disconnected areas. As with all human induced changes, historical modifications installed on the Otter estuary require vital management and maintenance and increasingly the changing climate is making it more costly and difficult to justify this. Recently highlighted by the 2018 floods which overwhelmed the anthropogenic drainage system and almost destroyed the old embankment completely.

1. Standing on the current embankment, created in 1800’s reclaim land for agriculture, among other uses.

Previously, the RRC had visited the site during the 2019 AGM, so it was great to be able to see the progress made from the planning, pre-works phase of the project – check out the previous blog post here. This ambitious and multi-faceted project has been the culmination of almost 20 years of planning and hard work and Mike’s knowledge and passion for its delivery and many benefits were clear. The European Union’s, Promoting adaptation to Changing Coasts (PACCo) were the main funding partner involved in the project, alongside the Environment Agency and Clinton Devon Estates.

The history of the Otter estuary has been remarkably well documented, by Clinton Devon Estates and their predecessors, as far back as the 1800’s. In 1809-1812, James Greene and Lord Rolle executed their cutting edge land reclamation plans by building embankments that cut off almost three-quarters of the original estuary extent and draining the floodplain, to provide more agricultural land for local tenant farmers. Other engineering works carried out over the 19th and early 20th century included; building aqueducts to carry tributaries over the floodplain and culverting others, creating a main trunk drain to convey water and sediment straight out to sea, creation of a refuse tip and converting an area into a cricket pitch for local people. All of these modifications adversely impacted the natural ability of the river and its floodplain to support biodiversity and attenuate flood water so that upstream, local settlements (e.g. Newton Poppleford and Otterton) have been increasingly affected by flooding incidences during high rainfall episodes, particularly compounded over high tides. With pre-modification estuary data and plans available, it was possible to see how the estuary could be returned to a more natural state by removing many of these anthropogenic structures, giving the river back its floodplain and allowing natural processes space and time to reinstate riverscape functions.

Many obstacles and challenges were overcome during the planning and implementation of this project. Below is a summary of some of the main issues. The context of the land-use and designations of the site provide the back-drop to the complex and diverse nature of the consideration needed during planning and implementation. The River Otter has numerous conservation designations including SSSI’s for saltmarsh and mudflat habitats and is situated in the East Devon AONB. Adding 55Ha of saltmarsh and mudflats to the current estuary offering of 33Ha, was of obvious benefit, however care was taken to ensure relocation occurred and limited disturbance of protected species (including dormice, beaver, bats and ring tailed plover) during heavy machinery works (photo 3). We were surprised to learn that some species are recovering already, despite heavy plant operations ongoing on site; sightings of the rare black tailed godwit, for example, increased from 6 in February 2002 to 106 in 2023.

2. Local wildlife has apparently had very little adverse effects during construction, showing careful construction working with nature is possible.

3. Current previous floodplain with heavy machinery building new footbridge for the South West Coast path and reconnecting the floodplain.

The shingle bar, located on the sea front, creating a narrow 15-20m outlet for the mouth of River Otter is designated as the UK’s only natural world heritage site and has changed very little over last few hundred years. Protecting the integrity of the shingle bar is an important aspect of the project. Buried within the bar is a South West Water owned, sewage outfall pipe which had to be relocated as part of the project, using directional drilling to future-proof the asset and mitigate for predicted change as natural processes reshape the estuary. This was a particularly costly addition to the project, but vital to secure waste management for the local population. It will be interesting to see the changes that will occur at the mouth of the estuary with the predicted tidal prism to be 2.5 times higher than the current, increasing velocities and leading to erosional processes in both lateral and vertical directions. Erosion will be monitored at the shingle bar and water levels monitored via surface radar at various sites further up the estuary.

Local amenities, including the cricket club and numerous public rights of way (the protected SW coast path travels along part of the embankment) were protected and in some cases relocated. The cricket club was relocated to another local area and tenant farmers were compensated with new farmland located nearby.