ABSTRACT

“The study highlights the importance of the South West coast line to Sri

Lanka, the problems and main causes of coastal erosion, and the current

strategy of the government relating to the erosion issue. The study

emphasises alternative solutions using innovative methods to overcome

erosion issues in the short and long term. The proposals focus on

dynamic areas like Hikkaduwa and Galle port, which are of major

economic significance.”

INTRODUCTION

Sri Lanka is an island nation, with 1620 km of coastline of which 300 km

are beaches and sand dunes (CCD, 2007) with various geomorphologic

features such as lagoons, bays, headlands and peninsulas. All these play

a vital role in the socio-economic development of Sri Lanka.

The South Western

coastline stretching

from Colombo to

Galle, constitutes

15 percent of total

land area, and is

occupied by 40

percent of the

population (CCD,

2007). Fishing,

tourism, trade and

manufacturing are

key economic

sectors in the SW

coastal region. According to CCD annual report 40 percent of the

country’s GDP and 70 percent of total industrial output comes from the

SW coastal zone. Coastal tourism for the region represents 80 percent of

the total tourism infrastructure in Sri Lanka. As a developing nation,

tourism is very important to Sri Lanka.

Coastal erosion was not recognized as a critical problem until the 20th

century due to lack of research and knowledge of the economic

implications of erosion damage, but today it has become one of the

country’s most formidable challenges due to the disruption of coast-based

activities which have high economic value. Additionally the coastal erosion

influences ecological values, which directly affects socio economic values.

Coastal erosion creates many socio economic issues. The largest

problem is the negative impact on the lives of people who live in low-lying

lands. Another issue is loss of valuable land and infrastructure where high

demand is created by increasing population and scarcity of land. Damage

to the cultural values of people who have settled in the region since

ancient times has also been observed in studies.

Unfortunately, it has been observed that most of the SW coastline has

been subject to erosion for many years and it is important to rapidly

identify the causes and propose sustainable solutions to reverse the

current situation.

EROSION ON SOUTH WEST COASTLINE

Beach erosion is when sand supplied to a particular coastal area is less

than what is carried away from that area. The key resources that nourish

the beach sand in Sri Lanka are sediment carried down by the rivers,

sediments from eroding coastal features and off shore sands brought on

shore.

The SW coastline has been identified as the highest eroded coastline. It

has been determined that natural actions, human activities, and biological

activity are the three major causes for coastal erosion. This coastline is

mainly subject

to SW

monsoon in

May to

September and

Inter monsoons

from April to

May, when the

area is

influenced by

wind climate

with moderate

wave height.

The monsoon

generated high

intensity waves

enhance the

erosion.

The dynamic

nature of the

shore line itself

influences

erosion. In

contrast to bay

and headland

coastlines,

straight coastlines are more vulnerable to erosion as they have little or no

major natural fixed erosion protection. Further erosion happens due to off

shore loss of sand created by sea level rise and extreme events like high

waves, high tides and storm surges which eventually result in cross shore

loss of sand.

Natural erosion is added to by human activities. A breakwater, which was

constructed north of Negombo as part of a project to build a fishing

harbour along the straight portion of coast is a good example of a poorly

researched and designed structure which resulted in washing away a

fishing village situated north of the breakwater.

Other examples of adverse human intervention are beach sand mining in

Panadura, Lunawa and Angulana areas reducing beach sand volumes

available for littoral process; river sand mining along the Nilwala, Gin

ganga, Kalau ganga and Kelani rivers reducing sand supply to the beach;

collecting coral from beaches and shoreface; and reef breaking or

dynamiting coral for fishing. These human activities reduce the volume of

beach material and damage the reef, which acts as a small buffer to the

wave erosion.

GOVERNMENT STRATEGY ON SOUTH WEST

COASTLINE

In September 1981 the Sri Lankan government published the Coast

Conservation Act. As required by the Act the Coast Conservation

Department (CCD) was established in 1983 to develop a coastal zone

management plan. In 1988, the Colombo coast protection scheme, the

Moratuwa coast protection scheme and the coast protective scheme for

the area between Beruwela and Weligama were all commenced by the

CCD as the initial major projects to protect the SW coast line (CCD,1990).

Since commencement of those major projects, there was no further

information about any other significant projects implemented by the CCD

until the tsunami strike in December 2004. After the tsunami disaster, the

CCD implemented a new Coastal Zone Management Plan, along with

Disaster Management Center. The key aims of the plan were to construct

the setback, reconstruct the coastal defense system, and rehabilitate the

sand dunes and green belt around the coast line before the SW monsoon

started.

CCD spent $15 million to reconstruct hard defense structures,

approximately 3km long, comprising revetments, groynes and offshore

breakwaters near the most significant areas such as Galle port and

Hikkaduwa tourist zone. As a developing country Sri Lanka could not

afford to lose these valuable assets. Even though the government spent

millions to construct the defense systems, it still failed to provide the

required erosion protection, because structures did not perform as

expected due to lack of technology, understanding about environmental

stability and poor planning. This failure highlights the necessity for a well

planned and engineered sustainable coastal management plan.

PROPOSALS

In the long run proposals for managing protection of the coastal line and

preventing erosion should be technically engineered to incorporate social,

economic and environmental factors to be considered a successful

sustainable solution. Each proposal should consider the current requisite

need of each location. In every case, it is important to consider the prime

elements or essence of immediate or long-term actions.

In a Sri Lankan

context, as a

developing country,

great care should

be taken in

selecting an

appropriate budget

for the proposal,

and determining

that the proposal is

able to recover the

cost thus gaining

optimal value for

the money.

Hard Engineering

and Soft

Engineering

solutions are the

two methods to

prevent beach

erosion. The hard

solution

incorporates

permanent

structures that

reflect or disperse

incoming waves

such as Sea walls,

offshore

breakwater, and

Groynes. Soft

solutions, which do

not involve

hardened

structures, include

natural interventions

such as beach nourishment, and sand dune stabilization.

The main concern of any targeted proposal is to protect the SW coast line

without disturbing the natural beauty of the area which is world renowned

for the beaches and attract many tourists. Therefore, it is necessary to

adopt methods that are harmonious with nature. The proposals put

forward for coastal erosion management in SW coastline combine hard

and soft engineering methods according the topology and nature of

identical places.

The natural green belt around Sri Lanka is the main protection for the

coastal line against erosion. However, the tsunami disaster and human

actions has reduced its efficiency and effectiveness.

Consequently, it is proposed to strengthen the green belt near the SW

coastline by enhancing the coral reef, increasing the density of

mangroves, and improving the sea vegetation. It is recommended to

initiate Environment Protect and Bio diversity Act incorporated with

CCD and UDA to minimize the human involvement in the deteriorating

green belt. The act should adopt parameters like restrictions on coral

mining, pesticide runoff from crop fields to reduce the nitrogen level,

removing mangroves and sea vegetations. Further, the act should initiate

the improvements on regenerating coral reefs, enhancing mangroves

habitat and sea vegetation. Reinforcing the green belt, which will be a

feasible project in the long run; can significantly reduce erosion and

simultaneously enhance the fish and shrimp harvest to boost the local

economy.

But, there are major issues to be addressed immediately, because the

main railway and highway infrastructure, which connects South and West

part of the island lies parallel to the Hikkaduwa coastal line which has

been subjected to erosion. Hence, it is wise to go for a fast track

economical process simultaneously with reinforce the green belt.

It is proposed to introduce an economically feasible method that can

reduce wave energy, ultimately avoiding sediment erosion in Hikkaduwa

coastal zone. It is a flexible breakwater system, which will be an

environmental friendly mechanism. Flexible wire nets and rings of

vehicle tires and soft blades on the surface are used in combination to

make this flexible device as in the figure no 4.

The flexible wire

net is held by the

stack of rings. The

deposition of

sediments in

coastal area and

reduction of wave

energy will mainly

be done by flexible

wire net. The

sedimentation of

coastal area

enhances the coastal vegetation process. This proposal will disturb the

natural appearance in the SW coastline, but considering the long run

economical and other advantages this would be one of the most optimum

methods. This innovative method was discovered by Fong Shin

Construction Co. China, which has become a more effective method as

shown in the figure no 5.

The Galle zone in SW coast line has to be treated in a special manner due

to strong waves and high tides. Therefore, it is recommended to construct

man made barrier reef. Even though the structure is costly, the expense

will have to be borne due to the economic significance of the area with

Galle port which is considered as the third capital in Sri Lanka.

Rubble can be used as the main material to construct the reef due to the

availability of the material in the area and it will tend to minimize cost. The

proposed structure will be constructed all along the Galle zone giving

ample space for vessels to enter the harbour.

The design should be enhanced to use the strong waves and high tides to

improve the surfability, which can help to boost up the economy while

protecting the shoreline from erosion. To focus and shape the breaking

waves in an attempt to improve surfability, there should be a good

understanding about the speed, height, and direction of the waves and

tides.

CONCLUSION

Erosion has become a severe problem for a small island with increasing

population and economical threats. Any erosion process cannot be

reduced to zero, but it could be minimized to some extent. Three

proposals have been formulated which should proceed simultaneously to

gain optimal results. The proposals were based on the few researches

and current data available. However, it was realized the essence of a

long-term strategy is harmonious with the proposals. The strategy should

include Regulations barring human activities and mandatory pre-

permission process, Education and awareness of the coastal habitat

system for key stake holders, Planning and Policy Development of

conservation of coastal habitat, Monitoring program for ongoing actions,

Research process on how global issues affect Sri Lankan coastal line,

Identifying pattern and nature of waves, tides around the island,

alternatives for the coastal protection systems and innovative methods to

enhance the natural habitat like coral reefs and mangroves, and proper

Coordination at national and local level in putting the long term strategy

into practice.

SHOULD WE ABANDON OR REBUILD COASTAL DEFENCES? CASE STUDY: THE SOUTH WEST COAST LINE OF SRI LANKA K.A.E. Alwis- Student No- 1132372

Reference :- Abbreviations :-

Coast Conservation Department., Sri Lanka's Agenda for Coastal Zone Management. Retrieved November 26, 2011, from http://www.coastal.gov.lk/showresearch.php?ankaya=11 SW – South West Coast Conservation Department., Economic Significance of Coastal Region of Sri Lanka. Retrieved November 26, 2011, from http://www.coastal.gov.lk/showresearch.php?ankaya=12 CCD - Coast Conservation Department Fong Shin Construction., we solve the coastal erosion problem. Retrieved November 25, 2011, from http://www.fosh.tw/ UDA – Urban Development Authority GDP - Gross Domestic Product

Figure 1 “Hikkaduwa Coastal Line”

Figure 2 “Erosion on Sri Lanka”

Figure 3 "Proposal Approach"

Figure 4 "Flexible Breakwater System"

Figure 5 "Flexible Breakwater Adoption in China"