Threats of coastline
1) coastal erosion, cliffs composed of rapidly eroding glacial deposits
2) wave energy, destructive waves remove sediment
3) tidal ranges of 5m increase flood risk
4) storm surges, increase erosion & flood risk
5) unintentional impacts of coastal development
6) climate change & sea level rise (6mm/yr)

Shoreline management plans (SMPs)
are documents that examine the risks associated with coastal processes and present a policy to manage those risks. they consider risks to local people as well as natural & build environment, the policy is drawn up with many local stakeholders.
The published SMP will
1) divide sub-cells into appropriate management units
2) identity economic & environmental assets, assess issues and conflicts, propose a defence plan
3) use DEFRA criteria for management
4) Intergrated Coastal Zone Management (ICZM), manage whole of coastal zone not just shoreline

DEFRA criteria
1) hold the line, maintain existing defences
2) advance the line, build new defences
3) managed re-alignment (retreat), allow flooding with managment
4) no active intervention, no investment

• a reduction in human intervention in a natural processes
• working with the natural processes rather than against them

Accessing the risks
1) Cost benefit analysis (evaluating the economic, social & environmental costs and benefits of the scheme)
2) Environmental Impact Assessment (assessing the impact of a project so damage can be minimised, will the environmental quality improve or decline based on the DEFRA strategy employed)

Sediment supply
Overstrand

• sediment volume decrease & erosion rates increase
• sediment trapping at Overstrand has caused sediment starvation downdrift
• reduces sediment volumes has increased rates of erosion as sediment no longer protects the toe of the cliff - accelerating removal and cliff retreat rates by undercutting and landslides increase

Summary of NE Norfolk coast

• characterised by less resistant geology, high wave energy & high rates of LSD
• coastal management (protection) is required to reduced the impacts of erosion and sea level rise
• the natural processes in the sediment cell have been disrupted by human activity (coastal defences):
  1) cliff protection by coastal defences has reduced erosion rates in key locations
  2) BUT, in many areas erosion rates remain high
  3) sedimentary budget calculations indicate the defences have caused sediment starvation on many beaches downdrift which has the potential to expose cliffs to increased erosion rates
  4) further management is required to halt the natural processes of coastal erosion

Overstand will be missing in the next 100 years if we do nothing

POLICY - hold the line

Hard engineering - building structures at the base of cliffs or on beaches
Soft engineering - work with natural processes in the coastal system as management

Predicted erosion losses of £34032k by 100 years

Summary
HTL - defences have intentionally the coastline
Flows of materials:
1) beaches are growing in volume, reducing gradients and increasing width
2) promontories (headlands: Cromer and Overstrand) are no long retreating due to protection yet reduce sediment inputs to the beach

• slope failure means cliff recession still going
  Flows of energy
  1) defence strategies reduce wave energies

Slope drainage
plastic or clay pipes in the slope, reduce pore water pressure and reduce weight on slope. however, often blocked, destroyed in slumps.

• Overstrand, reduce weight of cliff & reduces slumping and collapse

Storm surges
2m surge on high tide caused extensive flooding inland. Flooding of Broadlands caused environmental & economic (tourism) devastation.
Storm surges are caused by extremely high onshore winds, low atmospheric pressure and coastline shape

Tidal range = over 5m, increases flood & erosion risk
Fetch = 1500 miles (high energy environment, frequent storms)

1953 storm surge & flooding in Norfolk, earth embankment damaged after, rebuilt

POLICY - hold the line

• flooding of Broadlands would be an environmental & economic disaster
• 6000 hectares would be flooded

How is Sea palling defended

• earth embankement
• curved sea wall (added to embankment since 1954)
• stepped toe
• rip-rap (later addition due to undercut)
• embankment has flood gates

Offshore reefs

• management strategy, initially advance the line
• constructed with aim of reducing wave energy & protecting the beach for tourism & recreation
• medium term strategy, hold the line
• construction, built in 2 stages (first 4 in 1995, North, £5.9m), 450m apart, 2.8m above sea level, 321,000 tonnes of rock
  Why?
• built up beach reduces wave energy, safe tourism destination
• waves break offshore & energy reduced
• dissipates wave energy, reducing erosion
• expensive & difficult to install

Info

• handles 1/3 of the nations gas supply worth £1.7m per day
• sea defences put in place coast an estimated £18m
  

Intentional change - more reefs
in 1996, 5 more reefs built

• 180m long with gap of 160m to prevent erosion in gaps
• only 1.2m high than sea level to allow waves to pass over the top, to prevent tombolos
• used 220,000 tonnes rock & cost £10.5m

Bacton gas terminal located here

Has the project worked?
Overall effective, but not a long term investment as will be gone in around 20 years. In July 2021 wave action created a sand bar that breaks energy of the waves.

• Beachfront cafe owner says in past 15 years, cafe has flooded twice casing major damage, but now he no longer worries about weather
  

• shore platform, cliff, beach, scree / landslide
• oxidation, landslide, wave erosion (undercutting), cliff retreat

Reasons for rapid erosion

• rock type & structure, less resistant boulder clay which slumps when wet
• naturally narrow beaches, less protection as dont reduce wave power
• man-made structures, groynes have been installed to stop longshore drift & build up beach in certain places, narrows unprotected beaches elsewhere
• powerful waves, long fetch, high energy
• beach starvation, Bacton defences trap sediment further up coast promontory effect of the headland

wave refraction around sea wall causes increases erosion & may lead to cliff erosion & landslides

Economic development

• sand is an essential material in the modern economy as it can be used in construction, glass & concrete making and beach norishment
• a high-quality sand resource occurs in the nearshore zone at Mangawhai-Pakiri on the east coast of New Zealand's Northland Peninsula, it is suitable for the construction industry
• located just 50km north of Auckland, New Zealand's largest and most economically metropolitan area (1.5m population - 1/3 New Zealand's total - 35% total GDP, tourism focused on the coastline with 2.3m foreign visitors in 2015)

Offshore sand mining and the sediment budget

• nearshore sand dredging on the 20km coastline between Mangawhai and Pakiri has operated for over 70 years
• between 1994-2004, 165,000 metres cubed /yr was extracted
• mining ended in Mangwhai in 2005 but has continued at Pakiri beach
• current extraction rates are 75,000 metres cubed /yr until 2020, this sand is used to replenish Auckland tourist beaches
• sand is a non-renewable resource on the coastline, deposited during the Holocene (past 9000 years), coastal sediment budget is overall a closed system
• extraction rates at Pakiri beach exceed inputs by a factor of 5, the effect will deplete total sand supply

Impact on coastal landforms

• as closed sediment cell, current rates of sand extraction are unsustainable
• beaches starved of sediment have become wider & flatter & less effective at absorbing waves
• higher energy waves then erode the beaches
• foredune ridges are undercut by wave action, developing steep, seaward-facing scarps. loss of vegetation cover makes them susceptible to wind erosion
• 1978, storms caused 28-metre breach at the base of Mangawhai spit. this, and a second breach, altered tidal currents, leading to sedimentation of Mangawhai's harbour
• shallower water in harbour also threaten Mangawhai community with flooding, subsequent dredging of the harbour & groyne construction on the spit has helped restore some equilibrium
• coastal retreat is already evident & attributed partly to sand extraction

Hopton Holiday Village

• claimed it would have lost its first row of clifftop caravans & a second row in 2 years time had it not commissioned the work
• at the time sand levels at Hopton-on-sea were reported to have dropped by up to 10ft (3m) in 5 years
• 2014, Borne Leisure built 9 rock groynes at Hopton-on-sea with 54,000 tonnes of imported granite at a cost of more than £7m
• coastal erosion expert Dr Phillip Barber studied damage & said port was to blame as it changed tidal flow & littoral drift
• since 2010, Hopton beach lost between 20,000 to 40,000 cubic metres of sand each year

What is the delta like?

• a wave dominated arcuate delta composed of promontories separated by embankments
• beach forming a continuous coastal flat with dunes & lagoons at the distal end
• the delta was built from 7 distributies, most silted up leave 2 active channels: Rosetta & Damietta branches

a low energy coastline

3 delta landforms
upper delta - plain composed of river sediment, above tidal area
lower middle delta - inter-tidal zone composed of both river and marine sediment
submerged delta plain - below sea level and composed mainly or marine sediment

Why does deposition occur?
1) a shallowing river gradient causes velocity & energy to drop
or 2) high energy river (fluvial) entering low energy sea (here)

• decrease in volume of water channel
• flocculation, mixing of salt & fresh water

Important processes
slowing flow, mixing of fresh and salt water aids flocculation meaning all the small silt/clay particles are depositied
lower density, the river water has lower density and floats above sea water due to lack of salinity, river beds load deposited close to coast, suspended load well offshore

Unintentional impact of development
transition from a fluvial dominated growing delta to an eroding wave dominated delta

• the Aswan High Dam completed in 1964 to control flow of the nile, to generate electricity and to provide water for irrigation
• but the dam impacted sediment flux
• as result a great deal of effort has gone into constructing coastal defence struts to protect important sections of the coast of particular socio-economic importance

Sediment supply to the delta

• Aswan dams & irrigation schemes reduced discharge & sediment entering delta, reduced from 40 to 5 x10^9 metres cubed per year
• sediment load decreased from 200 million tonnes to 134 trapped in artificial resiviours
• irrigration schemes 10,000km of canals, low velocities, deposition of muds, entrapping sediment
• wetlands, swamps & lakes also trap sediment

Important factors for development of Nile Delta

• geology & structure (limited impact, sands & gravels)
• low wave energy (short fetch & swell window)
• low tidal range (restricted circulation)
• climate (semi-arid)
• human impact
• fluvial energy
• currents & waves

Sidestrand erosion rate 1885-1985 = -1.52, 2005-20015 = 0.98