West Cumbrian coast Flashcards
Location
NW England, county of Cumbria just below Scottish border, coast on Solway Firth, between Maryport and Silloth
Solway Firth
An estuary leading into the Irish Sea, a national landscape
Characteristics of coast
Flat, sandy beach so low energy, B5300 parallel to coast, not built up, agricultural farms
Geology
Allonby bay: harder St Bee’s sandstone bedrock, clay and silt deposits. Above: softer Mercia mudstone bedrock, harder sand and gravel deposits. Bay S as superficial deposits
Sediment sources
Headland erosion: St Bee’s S of Maryport and Dubmill Point to the N. Rivers: River Ellen out of fells
Sediment stores
Saltmarsh behind the Grune, Mawbray Banks psammosere, soft glacial deposits from glaciated environment, Allonby bay beach
Allonby beach
Drift-aligned beach as longshore drift so wide and long, lots of offshore sandbars (contributes to low energy beach), B5300 prevents some development
Mawbray Banks
SSSI and National Nature Reserve in Solway Coast AONB, Natterjack toad in dune slack, World Heritage Site as Roman fortifications at the end of Hadrian’s Wall, fences restrict cattle grazing
Waves
Small and low-energy: short SW winds fetch, shallow estuary <20m. Depositional landforms
Why does the area need protecting
Damaging storm waves can cause severe coastal erosion
What is there to protect in the area
Towns e.g. Allonby, B5300 washed away in 2018, Victorian intervention meant no sand dunes except Mawbray Banks, soft geology
Maryport to the Grune
In sediment cell 11, all except Grune hold the line. Hold the line protects B5300 and allows study of Dubmill Point effects. Do nothing allows spit’s natural evolutionary behaviour with few assets risked
11e4.1
HTL short to long term.
11e4.1 sea defences
Victorian sea wall built in 1930s protects Maryport and B5300. Very effective, tourism maintained with promenade. Beach levels dropped, recently overtopped
11e4.2
HTL short term, NAI from then on. Defence in reasonable condition, beach won’t lower as resistant bedrock exposed, may change based on cycleway plans
11e4.2 sea defences
Revetments built in 1990s. Informal and cheap as made from tipped material including broken concrete. Protects cycleway and B5300
11e4.3
MR short to long term, requires moving B5300 so current maintenance
11e4.3 sea defences
Gabions
11e4.4
Allonby. HTL short to long term although do minimum whilst Allonby at low risk
11e4.4 sea defences
Planned as only wide upper shingle beach backed by sand dunes
11e4.5
NAI short to long term
11e4.5 sea defences
May bolster temporarily as need more info on Dubmill Point and B5300. Groynes preserve tourism but are poor condition. Revetments are poor condition with holes, needing constant maintenance and refaced 2011
11e4.6
HTL short term, NAI medium to long term, depends on B5300 and Dubmill Point so temporary maintenance
11e4.6 sea defences
Same as 11e4.5. Rock armour enables HTL during consideration, but imported rock
11e5.1
HTL short term, MR medium to long term as waiting on Dubmill Point and B5300
11e5.1 sea defences
Rock armour built 2019 allows temporary HTL and protects Beckfoot properties and some heritage assets, but imported rock
11e6.1
Silloth Harbour. HTL short to long term as harbour walls need maintenance due to the outer Solway low water channel moving closer to shoreline so increasing wave energy
11e6.1 sea defences
Breakwater built in 1850s improves harbour conditions but causes shoreline retreat as cuts off natural sediment drift. Groynes built 1979 across whole beach, but poor condition and starves beaches further along
11e6.2
HTL short to long term as harbour walls need maintenance due to the outer Solway low water channel moving closer to shoreline so increasing wave energy
11e6.2 sea defences
Same as 11e6.1. Revetments and recurved sea wall work together to protect B5300 (still high risk) and tourists can access. Beach nourishment and management using crushed rocks and dredging from Silloth harbour in future to HTL
11e6.3
The Grune. NAI short to long term allows spit’s natural evolutionary behaviour with few assets risked
