Coasts Flashcards
The Sunderbans
Key info:
* Located south of India and Bangladesh
* Home to largest mangrove forest and delta in the world
* Extends 10,000km^2, 6000 in Bangladesh
* 4 million people live along the coastline
How do waves break
- Friction w seabed slows down the base of the wave
- Crest of the wave rises as it moves forward, velocity and wavelength decrease
- Increasingly eliptical orbit
- Wave steepens until it reaches a wave height: wavelngth of 1:7 where it’ll break
- Water rushes up beach as swash
What is the global conveyor belt?
surface and deep ocean currents that circulate the globe in a 1000 year cycle
it is the result of:
1. Warm surface currents carrying less dense water away from Equator towards poles
2. Cold deep ocean surface ocean currents carrying denser water away from the Poles toward the equator
distributes heat which regulates weather and climate and cycles nutrients and gases around Earth
(Feedback in a coastal system)
Management plans ensure natural balance at coastline by counteracting exacerbating impact of positive feedback systems that take them away from equilibirum
Constructive and destructive waves
Constructive :
* 8-10/minute
* they push material up a beach before depositing it
* wave front is gently sloping
*Strong swash and weak backwash
Destructive:
-10-14/minute
- Weak swash and strong backwash
Currents
Surface ocean currents:
* wind-driven and can be vertical or horizontal (i.e rip currents and upwelling
* Upwelling is where wind blowing across ocean pushes water away, water then rises from beneath to replace it, warm water that is taken away is pulled downwards and sinks
Deep ocean currents:
* density driven and slower moving
* carry deep ocean currents away from poles towards the equator
Morecambe and Heysham
Key facts
Heysham:
* population 17,016
* site of 2 nuclear stations
* large coastal village overlooking Morecambe Bay, area is dotted with ancient sites
Morecambe:
* pop of 34,768
* primarily a seaside resort on SE edge of Morecambe Bay, most of econ based on tourism,hospitality and catering
Beachy Head to Selsey Bill
Pagham Harbour + Cuckmere Haven
SMP: (Shoreline Management Plan)
Pagham Harbour:
* located in south coast of England, Cell 4
* Beachy Head to Selsey Bill is its own sediment cell, there are shingle beaches + spits
adopted policy of ‘Adaptive Management’ bc of designated nature of the area
in 2013 they constructed a rock revetment
Cuckmere Haven:
-suffers from sever storm damage, has large shingle and boulders
- Medium and long term policies within SMP 2 were for No Active Intervention
- they then followed with Managed Realignment after 2014 storms destroyed groynes and caused sea wall fractures
- then rebuilt seawall and introduced beach realignment
Major changes in sea level
- 18,000 BCE global sea level was **120m< **current levels as most of it was locked up in ice sheets and glaciers (Ice Age) in cryosphere
- Current sea level stabilised around 1000 BCE
- 20th century, 3.2mm/year from 90s to 2010, 3.3mm/year, in 2020 incr to 3.3 mm/year
- Could rise 50cm-1.5m by 2100
In last 10,000 years…
The Sunderbans (pt 2)
Impacts
Economic:
* Soil salinity is increasing as more of the coastline is being submerged, occuring in freshwater channels as well.
* Impacts incomes as freshwater fish and crop numbers decrease
* therefore greater food insecurity
Environmental:
* People are destroying mangroves for firewood, charcoal, and timber collection
* CYCLONE SIDR: 15th November 2007, wind speeds up to 260km/hour, 3500 deaths w quarter of mangrove damaged and many of the mangrove trees being uprooted
* Much of the mangrove area is being converted for intensive agriculture and settlement, particularly as pop is becoming even more densely populated
Social:
* Royal Bengal Tigers are danger to people, especially fisherman, increased poaching and fishing has meant that food sources and habitats are reduced significantly
* Lack of access to services such as healthcare/education and access to help/aid because of the size of the areas and that many of them can only be reached by water, adds pressure to area and means less aid to damage
Why are these impacts important and what can you relate them to?
The Sunderbans (part 3)
management strategies
Adaptation strategies:
1. New salt tolerant rice varieties that can survive being submerged in sea water for over 2 weeks (resilient strategy as well)
Resilience strategies:
1. ongoing USAID is restoring mangroves, began in 2014 w 200,000 saplings distributed to teams of villagers, planted during low tide, 450 hectares of mangroves have been restored, villagers are trained to look after the saplings and understand their importance
Mitigation strategies:
1. 2015 1000 multi-purpose cyclone shelters were built in vulnerable locations -> can be used as a shelter but also as community hubs or schools outside of cyclone seasons.
how will they help solve risks
**
Examples of submergent + emergent coastlines
Rias: Fowey estuary in Cornwall
Fjord: Sogne Fjord in Norway
Dalmatian coastline:Croatian Coast in the Adriatic
Raised Beaches: Scotland has some that are 8m,15m and 20m
Relict Cliffs: Prawle Point Devon
Tectonic sea level change: 9.0 Indian Ocean earthquake 2004 uplifted Sea bed by 15m, permanent change being 0.1mm
Sediment cells
11 in the UK and they are closed systems
- River thames to Selsey Ball
Risks to Morecambe
- January 1983 wave reflection wall overtopped for 20 min, 1516 properties were flooded and sea wall was breached and seriously weakened
- second wall had worked to keep 80% of floodwater out but not sufficient for future
- Decision then taken to develop soft defences
In 2009 study done that shows a 1m rise in sea levels could completely submerge Morecambe
Defences at Morecambe
- Rock Armour/Rip Rap: boulders of locally sources limestone placed among maj. of existing promenade and sea walls, 1km from western end to east of town centre, 436,000 tonnes of rock
- 10 fishtail breakwaters were built in front of town at regular intervals, million tonnes of locally sourced limestone used
Nov 2015:
£10m flood defence, wall measuring 1.1 miles to be replaced on Morecambe’s promenade as part of 6 year project, funded by EA and lancaster city council
19th Oct 2018:
* £10.8m wave wall opened
* will reduce flood risk to 11,400 homes and should last 100 years
* will reduce risk of flooding to major highway and promenade infrastructure
Between 1989-2007
cost £28m
