ROMPIN Coast

Transcription

ROMPIN Coast
2A5.10 C3S3M1 (Rompin)
The Rompin sediment compartment from the mouth of Sungai Rompin to Sungai Pontian is
6.3km long (Figure 5-136). This compartment is unique in that divergent drift takes place here.
From the zero point drift, littoral transport moves away in opposite directions. The length of
Rompin microcell could be increasing as the coastline extends into both river mouths. The
coastline near the river mouths is highly dynamic, constantly changing its form and pattern of
erosion and accretion, and spectacular changes in coastline positions have taken place. The
northern developed portion where Rompin Town is located contrasts greatly with the
undeveloped southern portion. Erosion is a major problem inside the river mouth and the old
town had to be relocated. The compartment is divided into Seratus, Hiburan Rompin and Kalung.
The northern part of the Hiburan-Rompin coast lies within Rompin Town Council whereas the
southern part is outside the Council boundary. According to locals, the entrance to Rompin is
shallow and fishing boats have difficulties navigating the channel, resulting in boats relocating to
Sungai Endau. The river mouth is being dredged currently to facilitate boat navigation. The
popular, recreational beach at Rompin represents the best managed beach in South Pahang
Figure 5-136. Coastal sectors of Rompin Coast
Four beach profiles were leveled and the beach sediments analyzed and the beach assessed for
quality in the last beaches (Figure 5-137, Figure 5-138). The eroding beach along the river was
nor assessed for quality.
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HIBP1
HIBP4
Figure 5-137. Beach profiles HIBP1 and HIBP4
HIBP2
HIBP3
Figure 5-138. Beach profiles HIBP2 and HIBP3
2A5.10.1 Seratus
The Seratus coast covers the southern bank of Sungai Rompin to the end of the newly forming
cuspate foreland, which started as a beach lobe (Figure 5-139). The littoral drift here, in contrast
to the northern sediment compartments, is northwards. As a result, the entrance to Sungai Rompin
is narrow because the old cuspate foreland had elongated into the river mouth. The foreland is
still widening and encroaching farther into the river mouth, as sands eroded from updrift are
deposited on the protrusion. The whole foreland formation is also migrating farther up the river.
The foreland is a complex of barrier-lagoons, with beach forests on elongate spits alternating with
active lagoons, fringed by mangroves However, a new protrusion is forming at the entrance to the
river. Scouring by river action has eroded the coast where a massive service apartment
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development of 208 units is taking place (Seratus). River mouth management presents a real
problem here as the coast is subjected to both river and wave erosion. As long as newly-accreted
land is alienated into private ownership without consideration of river mouth dynamics and as
long as a wide buffer zone is not set aside, the problem of shoreline erosion threatening property
and structures will continue.
Figure 5-139. Seratus cuspate foreland - 2000
The oblique aerial photograph of 2005 illustrates clearly the changing pattern of erosion and
accretion in Seratus (Figure 5-140). A formerly accreting coast started to erode, the whole belt of
beach forest was lost to the sea and two chalets, even before completion, was damaged by falling
trees and was in danger of being washed away. On the ocean side of the new development was a
widening beach colonized by young casuarinas but on the river side matured casuarinas were
toppling over and the beach was disappearing. The presence of old scarps behind the wide beach
shows the changing shore condition. In the past, sand was mined from the beach lobe to renourish
Pantai Hiburan Rompin beach and, more recently, for creating a wood ball course. Deep sand pits
are left behind from the sand mining. There is strong wind action and sands are being moved
inland, creating sand ripples on the upper beach. In places the beach is being cut back to form
prominent beach scarps, and during low tide crescent-shaped bars lie offshore.
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Figure 5-140. Pattern of accretion and erosion at Tanjung Seratus 2005
The highly dynamic nature of Seratus is illustrated in Figure 5-141. It is an actively accreting
coast, with land advancing northwards into the river mouth through the formation of spits and a
cuspate foreland. The spit recurves and intervening lagoon makes Seratus very interesting and
should e set aside as a nature reserve. Unfortunately land on the unstable spits is being alienated
into private ownership and being settled. During the last five years, part of the new protrusion on
which the service apartment is located is eroding back. The cut back is expected to continue
unless the coast is extensively defended by costly structures. This would be unnecessary with
more consideration of the changing coastline in development. A detailed analysis of coastline
change of Seratus is described in Chapter 7.
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Figure 5-141. The changing Seratus coastline
Two beach profiles were levelled in Seratus, HIBP1 on the eroding beach on the river side and
HIBP2 across the accreting beach on the ocean side. HIBP1 captures a sharp retreating scarp
behind a slightly concave beach face of 6.6 degrees (Figure 5-142). The narrow beach was about
18m wide. The crest of the scarp is about 2.6m, less than one metre above HAT. Wave
overtopping is common as observed in the field. The land surface behind the scarp crest is about
the level of HAT and subjected to tidal flooding. During low tide a incipient swash bar is exposed
about 22m out in the inter-tidal flat. The beach was littered with fallen casuarinas trees. The
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beach sediments (ROMS1) were coarse grained, an indication of some fluvial supply, moderately
sorted, very positively skewed and platykurtic.
ROMP1
23 Jan 05, SWL 1115
3
Slightly Concave Beach
Sl
2.5
Height in metre(RL)
2
HAT
1.5
HAT
scarp
MHHW
MHHW
1
fallen casuarina
0.5
Beach face slope 6.8˚
MSL
0
0
10
20
30
MSL
40
50
60
70
80
swash bar
-0.5
intertidal areas
-1
-1.5
Distance in metre
Figure 5-142. ROMP1-eroding beach
ROMP2 captures a series of embryo dunes in front of the old coastal scarp and a cliffed foredune
before dropping down to the slightly concave beach face of 5.8 degrees (Figure 5-143). In the
inter-tidal flat is a swash bar trapping an elongate depression as it migrates shoreward. The width
of the dune field is more than 100m wide, and sands were mined from the deposits. The slightly
elevated foredune protects the accreted terrace behind, which is about the same level as HAT,
from tidal inundation.
ROMP2
23 Jan 05, SWL 1045
3
Slightly Concave Beach Slope
2.5
foredune
2
Height in metre (RL)
HAT
HAT
embryo dunes
1.5
MHHW
MHHW
1
Beach face slope 5.8˚
0.5
MSL
0
0
50
100
150
swash bar
MSL
200
250
-0.5
-1
Distance in metre
Figure 5-143. ROMP2 - accreting beach
The beach sediments were medium grained, poorly sorted, negatively skewed and leptokurtic.
The wide beach was assessed as of good quality when considering all criteria.
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The various coastal features and activities of interest in Seratus are illustrated in a series of
photographs below. The spit-narrow lagoon system at the cuspate foreland is very interesting
geomorphologically and offers a wide range of features and habitats that make an interesting
nature area (Figure 5-144). This place is visited by the more adventurous who have to travel
along well hidden and occasionally half submerged track to enjoy the serene seascape of
casuarinas and mangroves.
Figure 5-144. Spit recurves and intervening lagoon-inside river Sungai Rompin
There is the contrasting eroding beach along the river front and the accreting beach on the ocean
front, demonstrating that beach conditions can change temporary over a short period and spatially
over a short distance (Figure 5-145)
Seratus eroding river side coast
Seratus accreting ocean side coast
Figure 5-145. Contrasting beach of Seratus
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Currently, the pressing coastal issue for Seratus is the massive river and ocean front Tetuan
Lucky Beach Development, which is going to change the character of the area (Figure 5-146). Its
success will bring economic benefits but shoreline erosion may present problems difficult to
resolve. It is also a case where a formerly problem-free coast can suddenly be transformed into a
critical erosion coast because of poor siting. The problem would not have arisen if due
consideration had been given to river mouth dynamics. The signboard displaying the project did
not list an EIA consultant, if any EIA had been carried out. A hotel of more than 80 rooms would
have required an EIA, but the Seratus development is described as for service apartments.
Figure 5-146. On-going Seratus development (Tetuan Lucky Beach) of 208 service apartments on
Lot 215
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The condition of the eroding river front coast and impacts on Seratus development is illustrated in
Figure 5-147. The service apartments are now exposed instead of being protected by beach
forests and sand overwash clearly indicates that the development is vulnerable to tidal inundation
although the buildings are built on a raised construction platform.
Seratus development threatened
Overwash sands
Figure 5-147. Erosion, overwash and impacts on Seratus development
2A5.10.2 Hiburan-Rompin
The Hiburan-Rompin coast is the most familiar to beach visitors, as it covers Pantai Hiburan
Rompin, the popular local picnic beach and the beach in front of the Rompin Beach Resort
(Figure 5-148). The whole coast is lined with an attractive wide beach, sustained by occasional
beach nourishment. There are adequate facilities for local visitors and more is being done with the
construction of a wood ball course to promote the sports. There is the occasional visit to the beach
by foreign visitors, who may stay overnight in their campervan on the beach. The coast is
characterized by a prominent offshore bar running along the whole sector. The coastal plain is
composed of beach ridges with intervening swales, originally occupied by swamps. Of interest is
the zero-point drift which is located about the area of Rompin Beach Resort. The drift moves
away from this point in opposite directions towards the two river mouths bounding the Rompin
sediment compartment. A carpet of Spinifex covers the old berm in front of the resort, reflecting
the presence of wind blown sands and low dunes. The coast is still largely undeveloped. The
latest tourism related activity is the extension of the resort seawards on the wide buffer zone.
Despite the new development, the construction setback is adequate.
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Figure 5-148. Hiburan Rompin beach
This stretch of coast is more stable and have only experienced limited coastline advance of about
30m from 1997 to 2005 (Figure 5-149). The recent advance is indicated by the Spinifex covered
berm in front of an old scarp. The recreational beach has largely been disturbed and evidence of
the recent coastal history is usually preserved along secluded coast as south of the resort.
Figure 5-149. Slight coastal advance Hiburan Rompin coast 1988-2005
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The beach profile levelled in across the recreation beach captures the presence of minor dunes in
front of the car park and to seaward is an old berm and beach face succeeded by the new linear
beach face of 4.8 degress (Figure 5-150). The inter-tidal flat and offshore bar was not levelled.
The crest of the minor dune stood at slightly less than 3m but still more than one metre above
HAT. Overtopping of the dune crest will bring the waves into the car park. There are however
several footpaths to the beach in which the waves can travel into the car park without overtopping
the dune crest. The beach sediments are medium grained, moderately sorted, nearly symmetrical
in skewness and mesokurtic. The beach was assessed as of good quality when considering all
criteria.
ROMP3
23 Jan 05, SWL 1225
3.5
Linear Beach Slope
3
2.5
minor dune
Height in metre (RL)
2
HAT
HAT
old beach face
1.5
MHHW
MHHW
1
new accreting beach
0.5
Beach face slope 4.8˚
MSL
MSL
0
0
20
40
60
80
100
120
140
160
-0.5
swash bar
-1
-1.5
Distance in metre
Figure 5-150. ROMP3
The beach profile in front of the resort showed a coastal scarp with a 15m wide berm in front
before dropping down to a clearly concave beach face of 3.9 degrees (Figure 5-151). The beach
sediments were medium brained, poorly sorted, nearly symmetrical in skewness and leptokurtic.
The beach was assessed as of good quality when considering all criteria and was ranked as the
third best beach in mainland, South Pahang.
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ROMP4
23 Jan 05, SWL 0925
3
Concave Beach Slope
berm
2.5
scarp
vegetation line
Height in metre (RL)
2
1.5
HAT
HAT
MHHW
MHHW
1
Beach face slope 3.9˚
0.5
MSL
0
0
MSL
20
40
60
80
100
120
-0.5
-1
Distance in metre
Figure 5-151. ROMP4
Selected coastal activities are shown in Figure 5-152. These are gill netting off the beach by
locals and the preparation of a wood ball course with sands taken from Seratus. According to a
local, the state of Pahang is adopting wood ball as it considers the state as the home of wood ball.
The best known course in the state is at Lanjut Resort, which was promoted the sport.
1. Gill netting off the beach
2. Preparing a wood ball course, with sands
taken from Seratus
Figure 5-152. Activities in Hiburan- Rompin
Selected coastal features are shown in Figure 5-153. These are the good quality beach in front of
the car park, the crescent series of bars exposed during low tide, the Spinifex covered berm and
the swash bar with intervening elongate depression.
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Recreational beach at Hiburan-Rompin
Crescent bars
Protective bars
Spinifex in front of Rompin Beach Resort
Figure 5-153. Coastal characteristics of Hiburan Rompin coast
2A5.10.3. Kalung
The short Kalung coast was not visited in the field and description is based on aerial photo
interpretation and observation from Kampung Kuala Pontian. The coast is undeveloped but a
track is being built and it is expected that land will be alienated soon, if it has not happened yet.
Locals were seen exploring the coast probably looking for their alienated land and pegs were
observed on the ground near Rompin Beach Resort. There is a small oil palm holding just south
of the resort. The coast has a narrow beach with fringing casuarinas. In 2000 the coast appears
stable with a beach in front but on the 2005 oblique aerial photographs, a large number of
casuarinas trees had toppled into the sea and there was no beach during high tide, with waves
attacking the remaining beach forest (Figure 5-154). There is no clear net drift direction and any
drift present is weak. Although the zero point drift lies somewhere here or slightly upcoast in the
Hiburan Rompin sector, its exact point is difficult to establish. The swash bars was also present in
2000 but appears to have been destroyed by waves by 2005
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Figure 5-154. Kalung coast (cat III), stable in 2000 was eroding badly in 2005 but without any
economic impacts because coast not developed
Towards the river mouth and inside it, the coast is a confusing complex of former river channels,
entrance bars and spits. Some of the old channels are still active while others have been
completely colonized by mangroves and other swamp vegetation. The channel is gradually
migrating south towards Kampung Pontian and the sequence of migration is illustrated in Figure
5-155. The drift into the river mouth is strong and currently a large spit is extending from the
northern river bank into the river mouth.
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Figure 5-155. Advancing Kalung coast at Pontian river mouth
The southward migrating mouth has resulted in the interesting phenomenon in which land
previously across the river mouth in Pontian is now part of Kalung (Figure 5-156).
Figure 5-156. Land ‘migrating’ from Pontian to Kalung, caused by shift in river mouth
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From Kampung Pontian the large expanse of sand trapped in the spit extending into the river
mouth on the Kalung coast can be clearly seen (Figure 5-157). A thick belt of casuarinas fringe
the coast and young casuarinas are colonizing the newly accreting sands on the spit.
Figure 5-157. Accreting Kalung coast and backing beach forest from Kampung Pontian.
Entrance to Sungai Pontian is very narrow and river flow is strong
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