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. 128 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 129 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. 130 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. 131 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 132 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. 133 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 134 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 215 135 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. 136 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 137 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. 138 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. 139 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 140 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. 141 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 142 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 143