Dawlish warren

What is Dawlish warren and why is it important?

(Composite) sand spit extending across the mouth of the Exe estuary

Is a natural barrier protecting the estuary from high-energy storm waves

Protects infrastructure like Plymouth to Exeter railway

Key information of the 2017 management scheme

Cost - £12 million

Provides $158 million in flood and erosion protection benefits

Over 250,000m3 of sand used in the beach recharge

Spit protects 2,900 properties

Importance - Warren crocus, 20,000 migratory birds Petalwort (Rare liverwort in dune stacks)

What is Langstone rock?

A historical headland made of Permian Breccia

1846 - Railway cutting isolated it from the main cliff line

Acts as a groyne, interrupting sediment flow that influences the depositional patterns that form the spit

Where are the boundaries of the sub-cell?

Holcombe to the south, Straight point to the north

What is Pole Sands?

Offshore sand bar that provides sediment to replenish the spit in summer when constructive waves transport it landward

What is Bull Hill?

Estuarine sandbank in the Exe estuary. Part of the estuary sediment system, sand and mud are deposited by tidal currents

What are the threats at Dawlish warren?

Coastal squeeze

Sea level rise (4mm/year) → waves attack further inland

Repeated storms with strong onshore waves and high spring tides

What are the impacts of the threats at Dawlish?

5m of dune face lost from 2013-14 with 6 consecutive storm events

December 2013 - storm surge caused breach along 280m of the spit at high water mark

Storm Atiah and Brendan undid the 2017 beach recharge at the proximal end of the spit - beach lowered by 3m

What hard engineering is there?

Rock armour, sea wall, and groynes

400 meter geotube to brace the neck of the spit - seen as ‘relic’ defences that interfere with natural processes

What soft engineering is there?

Dune stabilisation using fencing and marram grass

Periodic beach nourishment

Why is protecting Dawlish a struggle?

All schemes aim to ‘fix’ a dynamic landscape that naturally wants to migrate landward due to rising sea levels

What is being done to compensate for coastal squeeze?

New wetland habitats are being created further up the rattans shoreline

Includes the Lower Otter River wetland restoration scheme and Goosmoore nature reserve in Topsham

What is coastal squeeze?

When rising sea levels and coastal erosion put pressure on coastal habitats, but the habitat cannot move inland as it is blocked by human development OR physical barriers