Coastal Management the control of development in the coastal area according to an agreed criteria

Sustainable Coastal Management The coastal area should be used / developed in such a way that it does not compromise ( or adversely affect) the quality of the coastal environment for future generations

Coastal areas are dynamic and fragile Hence need for careful management

Coastal Management Strategies Limiting damaging activities Protecting coastal resources Restricting development in areas prone to natural disasters

1. Limiting damaging activities Eg of damaging activities: Blasting of corals to create channels for boats Clearing mangroves to develop fish farms Dumping waste into coastal areas Constructing docks, marinas Such activities interupt the functioning of natural systems

To BAN or LIMIT such activities? Banning is costly Govts try to limit the damaging activities Eg the management of sand dunes in Port Philip in Melbourne

Problem: Visitors to the beach trampled on the dune vegetation. Vegetation destroyed, sand is exposed and blown inland by the wind, affecting nearby houses. Solution: Authorities fenced off the dunes Access paths to beach built for visitors

Result / Impact: Positive: Sand dunes recovered Negative: fences make beach look less attractive (eye sore) visitors do not have access to all parts of the beach

2. Protecting coastal resources (eg fish) Aim is to stop coastal resources from depleting Problem: destructive fishing methods like blasting and poison fishing are used (especially in South east Asia) Solution: Setting up of marine reserves Marine ecosystems are protected and fish and endangered species can breed and thrive

Result / impact Positive: Eg Goat Island Marine Reserve in New Zealand has 14 times more snappers in the marine reserve than outside Negative: Opposition from local fishermen as their access to coastal area is reduced, hence reducing their income (long term good versus short term problems?)

3. Restricting development in areas prone to natural disasters People are attracted to coastal areas because these areas provide : food and building material attractive services like ports, housing, recreation But tsunamis, storm surges, etc cost a lot Eg the Tohoku Earthquake in Japan in March 2011 cost US$300b in damages

Policies to deal with threat to coastal areas: 1. Retreat or relocation of built structures away from coastal areas prone to natural hazards 2. Avoid establishment of new farms and housing on low-lying land (eg in Indonesia) 3. Defence of coastal areas against erosion (eg beaches in Neatherlands are monitored closely to check for long term erosion, and beach nourishment undertaken to protect these areas.

Coastal Protection Measures In coastal areas where wave energy is very strong Homes and facilities in coastal areas can get damaged by waves

Two types of measures Hard engineering methods Soft engineering methods

Soft engineering methods Use knowledge of natural processes to protect the coastal areas Does not involve building of physical structures These are much cheaper than hard engineering methods These are easier to maintain too But they last for less than 15 years Use ecosystem-based measures eg: Planting mangroves Stabilising dunes Beach nourishment Encouraging growth of corals

Hard engineering methods Concrete walls or structures are built to protect the coast These cost millions of dollars (expensive) They can last for 15 – 30 years, and used more often Examples are: Seawalls Groynes Breakwaters Gabions

COASTAL PROTECTION MEASURES SOFT ENGINEERING STABILISE DUNES PLANT MANGROVES BEACH NOURISHMENT ENCOURAGE CORAL GROWTH HARD ENGINEERING SEAWALLS BREAKWATERS GROYNES GABIONS and Tetrapods

SOFT ENGINEERING #1: BEACH NOURISHMENT

definition This involves adding large amounts of sand to a beach that is being eroded. This could come from another beach or dredged from the sea floor Eg the sandy beaches at Siloso and Palawan in Sentosa are the result of fine sand added to the coastal area.

Effective? The effects of beach nourishment only lasts for about 10 years. The cost is very high because beach quality sand is very expensive It is time consuming to bring in and dump sand onto the coastal area Regular maintenance is needed, so ensure the sand is not washed away Nearby coral reefs get suffocated as the sand is washed out into the sea.

SOFT ENGINEERING #2: Stabilising SAND DUNES

Definition A coastal dune is a ridge of sand piled up by wind on the coast. Dunes form as a result of vegetation trapping and stabilising the sand.

Usefulness It helps as a natural barrier to protect roads and houses against coastal erosion and flooding. It provides a habitat for many animals including migratory birds. BUT moving vehicles and people have damaged vegetation on the coast which causes the sand to be blown inland which can cover nearby towns Hence the need to stabilise dunes

Remedy plant grasses on the dunes, roots of the vegetation trap and bind the sand together. build fences and access paths, to prevent trampling, vandalism Problem: high cost of maintaining fences, planting Solution: increase public education through signboards, encouraging public to support initiatives to stabilise dunes. (develop positive public attitude)

SOFT ENGINEERING #3: encouraging CORAL REEF growth

Usefulness They protect the coasts against coastal erosion by reducing the speed of the waves. BUT human activities such as dynamite fishing, sand mining and land reclamation have destroyed a number of coral reefs. Water pollution also affects coral growth as it can only grow in clear waters.

Remedy In countries such as Malaysia, the government has banned fishing within certain protected area. In other countries, people have built artificial reefs to allow corals to grow. Eg in the Maldives a structure of welded construction steel rods placed off the coast of Ihuru. It is charged with low voltage electricity to speed up coral growth Success: corals here growing 3 – 5 times faster than normal, and coastal erosion is reduced

Problems Coral growth is slow – takes 20 – 30 yrs to see results Not all sites are suitable Need to ensure no problems of siltation

SOFT ENGINEERING #4: Growing MANGROVES

method People plant mangrove to protect the coast against erosion by strong waves and winds. Many mangroves have prop roots or kneed roots that anchor the trees firmly in the muddy soil.

Effective Studies have shown that places with mangrove trees suffered less damage during the 2004 tsunami that areas with mangroves. Hence the Malaysian government launched a project to plant mangroves to protect its coastline.

Hard Engineering Methods

1. Seawalls

Seawalls are usually built in front of a cliff or along a coast. These seawalls (made of concrete) absorb the energy of waves and protects against strong waves.

Disadvantages of seawalls As waves break against the seawall, the energy from the waves is redirected to the base of the seawall. This will result in strong backwash which erodes the base of the seawall, causing it to weaken and collapse. Eg seawall along coast of Drakes Island in England collapsed due to this It is very expensive to build seawalls (S$ 3 million to build 1km stretch of seawall)

Wave energy absorbed by breakwater Breakwaters Deposition of sediments behind the breakwater. Beach built up

2. Breakwaters Breakwaters (made of granite) are usually built off shore, parallel to the coast. (or with 1 side attached to the land) The waves will break against it before reaching the coast. Zone of calm water behind breakwater, which allows sediments to build up to form beaches So the coast is protected

A series of breakwaters Sand deposited behind

Disadvantages of breakwaters It is also expensive to build (more than S$ 1 million). This method is unable to provide complete protection as it leaves some areas of the coast unprotected. Eg breakwaters in Portland Harbour, England resulted in erosion and flooding problems. One solution is to build a series of breakwaters eg at East Coast Parkway in S’pore But it is unsightly, and adds to the cost

3. Groynes

A groyne is a low wall built at right angles to the coast. 3. Groynes A groyne is a low wall built at right angles to the coast. It prevents materials from being transported away by longshore drift. Groynes reduce wave energy and cause sediments to accumulate on the updrift side (the side of the groyne facing the longshore drift). If successful, groynes help extend beach areas

A sewage pipe at East Coast Parkway that acts like a groyne Sand deposited on one side of the groyne Direction of longshore drift

Disadvantages of groynes The beach on the other side of the groyne will be eroded. Eg the groyne along Sandy Hook in New Jersey, USA, caused so much erosion on the downdrift side that it was eventually demolished A series of groynes will prevent this problem but this will spoil the beauty of the coast. These are costly to build and maintain

Remedy Tips of groynes angled at 10 , depending on wind direction to reduce erosion on downdrift side Build a series of groynes to reduce erosion eg along the coast of Eastbourne, UK, the beach has been successfully maintained after the construction of a series of groynes

3. A series of groynes http://www.geography-fieldwork.org/images/coast/groynes.jpg

4. Gabions This refers to wire cages containing small rocks to form a wall to protect the coast against erosion. Built along coast or behind a beach to reduce coastal erosion

Success They weaken wave energy, hence reducing coastal erosion They absorb wave energy better than seawalls as water can filter through the rocks

Disadvantages of gabions Gabions can be easily destroyed by powerful waves during storms Wires rust easily Can be damaged by excessive trampling and vandalism (eg gabions at East Coast Park had to be removed due to vandalism) also ruin the natural beauty of the coastal environment. Costly to maintain

5. Tetrapods 4-pronged concrete structures to dissipate wave energy Stacked offshore, interlocked, allow water to pass over them, hence no backwash created http://t2.gstatic.com/images?q=tbn:ANd9GcRPQhRjdJkCvusecEntQNGoGH5zXVpdIII3PzBjSkWON3hKpPTvsQ

Usefulness: Problems: Can be positioned quickly as they are precast Not easily damaged by waves as they allow water to pass around them Successfully used at Crescent City, north California for many years Problems: Unsightly Expensive to build Dangerous to swimmers, surfers

c. Case study: East Coast Park Image: ©Sengkang/Wikimedia Commons

c. Case study: East Coast Park Uses of East Coast Park: The Park was reclaimed to alleviate problem of land shortage in the 1970s Recreational activities such as swimming, fishing, cycling, jogging, kite-flying Used for sports events. Sporting facilities developed in the same area View TB for more details Image: ©Sengkang/Wikimedia Commons

Value of protecting coastal environment c. Case study: East Coast Park Value of protecting coastal environment East Coast Park’s coastline is near residential area (100m from coastline) Population is vulnerable to changes in coastal environment in the long run Image: ©Sengkang/Wikimedia Commons

c. Case study: East Coast Park Measures adopted to protect the coastline On reclaimed land Hard engineering strategies (seawalls & breakwaters) were put in place to protect the coastline from coastal erosion 4,500m seawall with a strip of pebbles, sand, clay and silt in front of it Two types of breakwaters used to protect the coast and create beaches: gabion and riprap breakwaters Large drains acting as groynes built on the foreshore What are the problems that arose from the application of hard engineering strategies on the East Coast Park coastline? Refer to TB for more details. The problems are: Severe erosion at the base of the seawall making it unstable and ineffective High maintenance cost for the seawalls, therefore not a practical measure Vandalisation of gabion breakwaters

c. Case study: East Coast Park Factors undermining the success of the coastal protection measures Sediments from the Johore shoal reduced due to reclamation of land at Changi for Changi airport construction Sinking of reclaimed land of East Coast Park due to lack of beach material; more vulnerable to erosion Extreme high tide events worsened erosion; sand from beaches washed landward Responses Beach nourishment, breakwater reconstruction Constant maintenance

CHAPTER 1 COASTS Should Coastal Environments Matter? In this Chapter, you will explore three key questions: How and why are coastal environments different and dynamic? Why are coastal areas valuable? How can we manage coastal areas in a sustainable manner?