Coasts AS Revision

COASTS ManagementImportanceErosionSand DunesWavesClassificationLandformsTransportation

Importance Why are costs important?

Economic sites for industry and fishing Economic sites for industry and fishing Habitats and ecosystems Habitats and ecosystems Tourism and recreation Tourism and recreation Coastal Protection Coastal Protection Defence and development Defence and development

Inter Coastal Zone Management 1992 – Earth Summit (Agenda 21 Ch.17) Protection of the Oceans 1992 – Earth Summit (Agenda 21 Ch.17) Protection of the Oceans Climate Change Climate Change 1993 – World Coast Conference 1993 – World Coast Conference All of these and more have pointed to the need for sustainable management of the diverse issues affecting coasts today All of these and more have pointed to the need for sustainable management of the diverse issues affecting coasts today

Successful ICZM requires 3 stages Successful ICZM requires 3 stages Stage One – Development and understanding of systems and processes Stage One – Development and understanding of systems and processes Stage Two – Use knowledge to create a sustainable long term environmentally acceptable plan Stage Two – Use knowledge to create a sustainable long term environmentally acceptable plan Stage Three – Implementation and enforcement as well as education Stage Three – Implementation and enforcement as well as education

Waves Oceans cover 70% of earth’s surface Oceans cover 70% of earth’s surface Coast is the narrow overlap between land and sea Coast is the narrow overlap between land and sea Waves and tides are used to divide the coast into zones Waves and tides are used to divide the coast into zones

Waves In Deep Water Swell – Often travelled large distance Swell – Often travelled large distance

Shallow Water Waves when the depth is less than one twenty-fifth of their wavelength when the depth is less than one twenty-fifth of their wavelength water particle orbits inside the wave become elliptical rather than circular as the “up-down” component of the motion is “squeezed” by the presence of the bottom water particle orbits inside the wave become elliptical rather than circular as the “up-down” component of the motion is “squeezed” by the presence of the bottom

Breaking Waves Spilling breakers Spilling breakers Plunging breakers Plunging breakers

Wave Refraction

Tides Oscillations of the sea surface Oscillations of the sea surface Tidal movements Tidal movements Tidal movements Tidal movements

Erosion Action of the waves Sub Ariel processes

Sub Ariel Those from above Those from above Wind Wind Rain Rain Cold Cold Heat Heat Human Human

Factors Effecting Rates Of Erosion Breaking Point of Wave Breaking Point of Wave Wave Steepness Wave Steepness Depth of Sea – length of fetch and shape of coast Depth of Sea – length of fetch and shape of coast Supply of beach material Supply of beach material Beach Width Beach Width Lithology Lithology

Transportation

Longshore Drift

Landforms Landforms are created by erosional processes Landforms are created by erosional processes

Wave Cut Platform

Tombolos

Barrier Islands Develop on coasts with high energy waves and low tidal ranges Develop on coasts with high energy waves and low tidal ranges

Formation Seen on eastern coast of North America, where they extend from New England south to Mexico. Seen on eastern coast of North America, where they extend from New England south to Mexico. long, narrow, offshore deposits of sand or sediments that parallel the coast line. long, narrow, offshore deposits of sand or sediments that parallel the coast line. formation of barrier islands is complex and not completely understood formation of barrier islands is complex and not completely understood current theory is that barrier islands were formed about 18,000 years ago when the last Ice Age ended current theory is that barrier islands were formed about 18,000 years ago when the last Ice Age ended glaciers melted and receded sea levels rose, flooded areas behind the beach ridges glaciers melted and receded sea levels rose, flooded areas behind the beach ridges rising waters carried sediments from those beach ridges and deposited them along shallow areas just off the new coast lines rising waters carried sediments from those beach ridges and deposited them along shallow areas just off the new coast lines Waves and currents continued to bring in sediments Waves and currents continued to bring in sediments In addition, rivers washed sediments from the mainland that settled behind the islands and helped build them up In addition, rivers washed sediments from the mainland that settled behind the islands and helped build them up

Barrier islands serve two main functions: 1. they protect the coastlines from severe storm damage. 2. they act as habitats that are refuges for wildlife

Factors affecting landforms

Rock Structure and Shape

Sand Dunes They grow when sand is deposited on the beach by longshore drift or shoreward movement of sediment sand accumulates into ridges which originally lie parallel to the direction of the prevailing winds They grow when sand is deposited on the beach by longshore drift or shoreward movement of sediment sand accumulates into ridges which originally lie parallel to the direction of the prevailing winds Sand dunes are dynamic elements of the landscape Sand dunes are dynamic elements of the landscape

Pioneer Stage - Foredunes pioneer species form on dunes. Tolerant of salt such as Marram grass pioneer species form on dunes. Tolerant of salt such as Marram grass They stabilize new dunes with their networks of root systems. They stabilize new dunes with their networks of root systems. Each plant can also spread sideways by up to 3 metres a year, helping to trap the sand and keep it in one place. Each plant can also spread sideways by up to 3 metres a year, helping to trap the sand and keep it in one place.

Yellow (White) Dune Stage begin to show a greater diversity of plants as conditions become more favourable begin to show a greater diversity of plants as conditions become more favourable As plants die and decay, a humus layer builds up and this traps both water and nutrients As plants die and decay, a humus layer builds up and this traps both water and nutrients more shelter and less salt spray. Marram usually still dominates the vegetation more shelter and less salt spray. Marram usually still dominates the vegetation Plants may include creeping fescue, sand sedge, mosses, lichens, sea holly and sea spurge Plants may include creeping fescue, sand sedge, mosses, lichens, sea holly and sea spurge dunes by this stage may well have reached 5-10 metres in height dunes by this stage may well have reached 5-10 metres in height Rabbits and other mammals may add their droppings to help enrich the developing soil Rabbits and other mammals may add their droppings to help enrich the developing soil

Grey Dune Stage much more stable, mosses and lichens fill the remaining spaces vegetation cover may reach 100% much more stable, mosses and lichens fill the remaining spaces vegetation cover may reach 100% Marram grass becomes less common Marram grass becomes less common Red fescue, sand sedge, sea spurge begin to dominate Red fescue, sand sedge, sea spurge begin to dominate Small shrubs (gorse, buckthorn) appear for the first time Small shrubs (gorse, buckthorn) appear for the first time metres from the sea metres from the sea humus begins to darken the surface layers a true soil begins to form humus begins to darken the surface layers a true soil begins to form commonly 10 metres in height and wider than those dunes nearer the shore commonly 10 metres in height and wider than those dunes nearer the shore

Dune Slacks dune slacks are found in between the more mature dunes where the water table reaches the surface causing seasonal or even permanent waterlogging and surface water dune slacks are found in between the more mature dunes where the water table reaches the surface causing seasonal or even permanent waterlogging and surface water Plants which are well adapted to these damp, sheltered hollows include rushes, sedges, cotton grass and creeping willow. If decay is slow, a peaty soil may develop Plants which are well adapted to these damp, sheltered hollows include rushes, sedges, cotton grass and creeping willow. If decay is slow, a peaty soil may develop

Mature Dunes Most found several hundred metres from the shore Most found several hundred metres from the shore these dunes develop a soil which can support shrubs and trees these dunes develop a soil which can support shrubs and trees Humans may plant fast-growing conifers which flourish in the sandy soil Humans may plant fast-growing conifers which flourish in the sandy soil

Fragility

Coastal Classification Johnson 1919 Emergent – fall in sea level Emergent – fall in sea level Submergent – rise in sea level Submergent – rise in sea level Stable – no change Stable – no change Compound – mixture of two of the above Compound – mixture of two of the above

Shepard Primary – Influence of sea is minimal: (fjords [Glaciers], deltas [Rivers], islands Volcanic]) 2. Secondary – Marine processes dominate e.g.. Headlands and bays, spits etc

Valentin 1952: 1. Advancing – marine depositation or uplift of land dominates 2. Retreating – Where marine erosion or submerging land dominates

Sea Level Rise Thermal Expansion of the oceans – warmer water is less dense than so occupies greater area Thermal Expansion of the oceans – warmer water is less dense than so occupies greater area Melting of small alpine glaciers Melting of small alpine glaciers

Tectonic Coasts Inman and Nordstrom 1971: 1. Diverging plates - Red Sea 2. Converging plates – Island arcs Japan and Philippines 3. Major transform faults - California 4. Stable plate boundaries – India and Australia

Energy Produced Coastlines Davis 1980 High Energy environments – Where destructive waves are more typical High Energy environments – Where destructive waves are more typical Low energy environments – Where constructive one prevail Low energy environments – Where constructive one prevail Protected Environments – Wave action is limited Protected Environments – Wave action is limited

Coastal Management

Case Studies Holderness – Coastal Erosion Holderness – Coastal Erosion Formby Sand - Dunes Formby Sand - Dunes N. Carolina - Barrier islands N. Carolina - Barrier islands