UNIT 4 (Sustainable Management of River & Coastal Landscape)

• Water cycle


  1. Transpiration + Evaporation

  2. Condensation

  3. Precipitation

  4. Surface runoff
• Drainage basin


  The river basin system is the part of the hydrological cycle which operates on the land. The system is an open cycle, this means the cycle consists of: Inputs - Water entering the system for example precipitation, Flows or transfer - Movements through the system for example through flow, Stores - Where water is held for example soil moisture storage, Outputs - Where water leaves a system for example evaporation
• Parts of drainage system


  • Upper stage
  • Middle stage
  • Lower stage
• Types of erosion


  • Hydraulic action - Erosion caused where air and water is forced into gaps in rocks or soil
  • Attrition - Where rocks smash against each other making them smaller and more rounded
  • Corrasion - The wearing away of the land caused by friction; rivers or waves carry sand or pebbles which erodes the land (sandpaper effect)
  • Corrosion - The wearing away of the land by chemical processes
• Types of weathering


  • Mechanical weathering (physical weathering) - this involves the break of rocks without any chemical changes taking place. This includes the power of water, wind and ice. Freeze-thaw weathering is when water gets trapped in rocks, expands and enlarges the crack
  • Chemical weathering - A chemical change occurs when weathering takes place. Rain water is slightly acidic and can slowly dissolve certain rocks and minerals
  • Biological weathering - this involves the actions of plants and animals for example plant roots will grow and expand into cracks in rock. Rabbits can burrow into weak rocks
• Types of transportation


  • Suspension - Small particles (sand/silt) float in the current
  • Traction - Larger stones are rolled along the river bed
  • Solution - some minerals in the rock are dissolved and carried along in the water
  • Saltation - medium stones are bounced along the river bed
• Deposition


  When material carried in the water is put down due to a lack of energy
• Main landforms along a river

  • Waterfalls (Upper stage)
  • Meander (Middle stage)
  • Delta (Lower stage)
• Factors affecting river flood


  • How permeable the soil is
  • How permeable the underlying rock is
  • How previous - previous rocks have joints and cracks within the rocks that allow water to pass through
  • Relief of the drainage basin
  • Type and amount of precipitation
  • Season
  • Vegetation
  • Human activity
  • High tides
  • Drainage density
• Flood graphs


  Peak rainfall - the time of highest rainfall, Peak discharge - The time when the river reaches its highest flow, Lag time - The time it takes for the water to find its way to the river between peak rainfall and peak discharge, Rising limb - shows the amount of water (discharge) entering the river is increasing, Falling limb - shows the amount of water (discharge) entering the river is decreasing
• Flood protection vs Flood prevention


  • Flood protection : Does Not necessarily stop flooding, but prepares people better against it (building homes on stilts)
  • Flood prevention : Actually stops certain areas from land flooding
• Hard engineering flood management methods


  • Dams
  • Flood relief channels
  • Levees/embankments
• Soft engineering flood management methods


  • Reforestation/afforestation
  • Floodplain zoning
  • Flood warning and preparation
• Case study 1 - Flood management along the River Yangtze

  Hard engineering: The Three Gorges Dam, Levees and embankments

  Soft engineering: Washlands, Land use zoning and flood warning systems, Conservation
• Coasts: Coastal process: weathering - erosion
• Floodplain zoning (soft engineering)


  • Buildings and land that is expensive would be located away from the river, areas next to the river would be able to flood as they are zoned to be green places and less claims for insurance
• Floodplain zoning (soft engineering)


  Not always possible to develop old urban areas into new zones, doesn't prevent flooding, some people might not approve of the zone methods
• Flood warning and preparation (soft engineering)

  • People will know when to protect their houses, with methods such as sand bags, they will also know when to leave, people can have their houses and businesses insured
• Flood warning and preparation (soft engineering)


  Not all people have access to the methods of warning and it doesn't stop the flooding
• Hard engineering for flood management along the River Yangtze


  • The Three Gorges Dam
  • Levees and embankments
• Soft engineering for flood management along the River Yangtze


  • Washlands
  • Land use zoning and flood warning systems
  • Conservation
• Coastal process


  Weathering - erosion (hydraulic action, corrosion, corrasion, attrition) - waves
• Destructive waves


  • Cause more erosion as it drags out sand more than it carries to the beach
  • Weak swash and strong backwash
  • Tall waves and short wavelength
• Constructive waves


  • Build up beach by deposition of material brought up in wash
  • Strong swash and weak backwash
  • Long wavelength and shallow gradient waves
• Transportation and longshore drift


  Material is moved along the beach in a zigzag way
• Formation of a headland and bay


  1. Wave refraction: when a wave bends around an obstacle

  2. Concordant - Only one type of rock creating a straight coastline

  3. Discordant - Many types of rocks alternating creating headlands and bays
• Formation of a spit


  1. Material is moved along the beach in a zigzag way (longshore drift)

  2. Deposition happens when coastline changes direction because of the curve of the coastline

  3. Headland creates shelter

  4. Waves lose energy

  5. Spit is cut off and salt marsh is created
• Formation of a wave-cut platform

  1. High tide causes abrasion, hydraulic action and corrosion on a cliff

  2. Over time the cliff keeps eroding creating a wave cut platform which you can only see when there is low tide

  3. Cliff will collapse as there is nothing to support it under it leading to cliff retreat
• Formation of CASS (cave, arch, stack, stump)


  1. First cracks in the base of the headland are enlarged through hydraulic action

  2. Cracks enlarge by weathering processes such as salt crystallization

  3. Cave is formed through abrasion and hydraulic action as crack widen

  4. Arch is formed when two caves are aligned, wave cut notches widen the arch

  5. Arch collapses under its own weight forming a stack

  6. Wave cut notches will form and the stack will collapse forming a stump
• Coastal management strategies


  • Do nothing - allow gradual erosion
  • Hold the line - Use hard engineering to protect the coastline or add extra sand to a beach
  • Retreat the line - Creating an area allowing land to flood naturally between low and high tides
  • Advance the line - Build new coastal defences further out to the sea
• Hard engineering methods


  • Sea wall
  • Sea wall with steps and bullnose
  • Groynes
  • Rock armor/ riprap
  • Revetments
  • Gabions
  • Offshore breakwater
• Soft engineering methods


  • Beach nourishment
  • Dune regeneration
  • Marsh creation/managed retreat/retreat the line
  • Set back
• Kite beach in Dubai


  • Beaches in Dubai were subjected to erosion because of other off shore developments (The Palm) - blocks prevailing wind preventing waves moving sand along the coast to kite beach - this leads to the loss of large parts of the coastal areas threatening the safety of buildings and infrastructures near the sea and preventing further developments along these beaches
  • Solutions were beach nourishment and groynes
• Groynes in Kite beach, Dubai


  • Successful in preventing longshore drift, in addition to that, beach nourishment also helped widen the beach making it attractive to tourists and accessible for swimming and beach sports. The project was successful in preserving the tourist attractions along the beach and keeping nearby residents safe
  • Expensive (35 million dirhams), prevents further developments on the beaches. Dubai reached the top of the list on the 2019 city beach break index. (Attracted 17 million tourists in 2019)
  • The increase in tourism allows business to thrive, making opportunities for the development of services such as cafes, restaurants, cycling and running track, parks and other attractions. This also creates job opportunities for people and contributes to the positive multiplier effect
  • The groynes were successful in preventing longshore drift and preserving the beach and helped protect the coastline and developments along it, which is an environmental advantage
  • Groynes are not natural looking, they prevent prevailing wind and starve beaches further along the coast causing faster erosion, prevent access along the beach in some parts, beach nourishments in particular areas needs to be replaced regularly, the project was expensive and is not long term, the project does nothing to protect marine life
• Dubai Mangrove Forest - Jebel Ali


  • Mangroves are trees that live along tropical coastlines rooted in salty sediment
  • Their lower trunks and above ground roots are submerged in seawater
  • Act as barrier to waves, slowing down coastal erosion
• Dubai Mangrove Forest - Jebel Ali


  • Protects the coast and residential land nearby
  • Education and spreading awareness (app made to allow people to track mangrove growth to engage the public with this project)
  • Sustainable Tourism that is eco friendly
  • Cheaper than beach nourishment and groynes, protects land and infrastructure reducing the need for maintenance and reconstruction
  • Mangroves are carbon sinks, provide habitat and breeding grounds for local wildlife species like endangered turtles and 40 species of birds
  • To protect the wildlife for now visitors will be made by invitation only (focusing on educational school trips and corporate team building)
  • The location is a United Nations reserve and the initiative in line with Dubai's plan for more than half of the emirate to be transformed into natural reserves by 2040. So politically the project creates a positive reputation for environmental sustainability in Dubai, UAE as this part of the world is known for its contribution to environmental harm from oil and industries