Calstock flood defence improvement scheme
Updated 26 September 2023
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This publication is available at https://www.gov.uk/government/publications/calstock-flood-defence-improvement-scheme/calstock-flood-defence-improvement-scheme
Background
An embankment in south-east Cornwall has historically played an important role in reducing flood risk to the village of Calstock. Recent surveys conducted by the Environment Agency showed it was in a poor condition. The embankment was at risk of collapse and preventing important habitat from adapting to climate change and sea level rises.
To address these issues, the Environment Agency has constructed new flood embankments inland, enabling the creation of a new 12 hectare area of intertidal habitat.
Aerial photos of the embankment area in 2022 compared with 2023. The 2023 image shows the intertidal habitat evolving (credit: Plymouth Marine Laboratory).
The new habitat will:
- increase biodiversity
- help adapt to the impacts of sea level rise and climate change
- help clean the Tamar Estuary by trapping sediment
The changes will also attract a wider range of birds and other wildlife which locals and visitors can come and see.
The new embankments
The Environment Agency has built over 600 metres of new earth embankments set back from the river.
The embankments were built using local material dug from the creeks and pools in the inter-tidal area. These new embankments now protect properties and important infrastructure from flooding.
The North Spur in November 2022 (credit: Pete Thompson).
Intertidal habitat and flood resilience
As in many of our estuaries, climate change and rising sea levels in the Tamar are leading to coastal squeeze. This means the habitat is prevented from adapting and moving towards land by a man-made structure such as a wall or bank. This leads to a reduction in important habitat for flora and fauna and feeding areas for birdlife.
During low tides in November 2021, a gap or breach was made in the old flood bank at Calstock. Water from the estuary was allowed to flow into pools and creeks which were constructed as part of the habitat creation. This has allowed the vital intertidal habitat to develop, with benefits for:
- wildlife
- the wider community
- carbon sequestration (higher-level saltmarsh and silt deposits capture, secure and store carbon dioxide from the air. This process shows good potential for reducing the human carbon footprint in the area)
Changes to wildlife in the area
A management plan for the site has been created in order to monitor which wildlife will begin to use the area as it transitions from field to intertidal habitat. This includes monitoring fish and plants. It will also hopefully include surveys of newly deposited mud in order to identify potential food sources for visiting birds.
Photo of a juvenile European smelt (credit: Pete Thompson).
This rare and protected juvenile European smelt was caught and released unharmed during surveys in the wetland. This survey also included catches of bass and mullet. This shows that fish species are using the site for feeding.
Over 30 bird species have been identified including:
- little egret
- kingfisher
- snipe
- teal
- green sandpiper
- reed bunting
- avocet
- water rail
The common sandpiper, whose numbers have declined in the UK were also spotted in the wetlands recently utilising the newly created habitat.
Photo of a water rail (credit: Pete Thompson).
Photo of a green sandpiper (credit: Pete Thompson).
Photo of a greenshank (credit: Pete Thompson).
Invasive non-native species will also be monitored to ensure they do not become established and damage the potential of the site. Casual observations of other species such as otters and beavers will be recorded as the habitats develop. Bat surveys will also be undertaken to determine improvements for bat foraging in what was once a poor site for insects.
Working with the local community
The Environment Agency has supported the local community in having access the former flood banks. This has involved the construction of a footbridge by Tamar Community Trust which links the two ends of the former flood defence embankment for walking.
The scheme has also made the field next to a local football pitch available to the community for recreational use and to generate funds for the community.
The Environment Agency thanks the community and partners for their continuing support. These include:
- Tamar Community Trust
- The Tamar Valley Area of Outstanding Natural Beauty
- Calstock Parish Council
Funding
The £3 million project was funded by:
- the government, via a flood defence grant-in-aid
- Water Environment Investment Fund
- contributions from the Tamar Community Trust
Intertidal habitat projects in the Tamar estuary
Calstock is one of three new intertidal habitat sites being created in the Tamar Estuary in 2021 and 2023.
You can read more about the other 2 projects in the area:
Contact
For further information email the Devon, Cornwall and Isles of Scilly customer enquiries mailbox at DCISEnquiries@environment-agency.gov.uk.