Coastal Erosion Prevention Research Articles

An investigation on the formation of submerged bar under surges in sandy coastal region

Cross-shore sediment transport rate exposed to waves is very important for coastal morphology, the design of marine structures such as seawalls, jetties, breakwaters etc, and the prevention of coastal erosion and accretion due to onoff shore sediment transportation. In the present study, the experiments on cross-shore sediment transport are carried out in a laboratory wave channel with initial beach slopes of 1/8, 1/10 and 1/15. By using the regular waves with different deep-water wave steepnesses generated by a pedal-type wave generator, the geometrical characteristics of beach profiles under storm conditions and the parameters affecting on-off shore sediment transport are investigated for the beach materials with medium diameters of d50=0.25, 0.32, 0.45, 0.62 and 0.80 mm. The offshore bar geometric characteristics are the horizontal distances from the shoreline to the bar beginning (Xb), crest (Xt), and ending (Xs) points, the depth from the bar crest to the still water level (ht), and the bar volume (Vbar). The experimental results have indicated that when the deep-water steepness (H0/L0) increased, the net movement to seaside increased. With the increasing wave steepness, the bars moved to widen herewith the vertical distances from still water level to the bar beginning (Xb), crest (Xt) and ending (Xs) points and the horizontal distances from the coast line to the bar beginning, crest and ending points increased. It was also shown from experimental results that the horizontal distances from the bar beginning and ending points to the coast line increased with the decrease of the beach slope. The experimental results obtained from this study are compared with previous experimental work and found to be of the same magnitude as the experimental measurements and followed the expected basic trend.

연안침식방지를 위한 관리체계 개선방안

Recently, coastal erosion has become an important issue in relation to keeping territorial integrity of a nation as well as protecting the coastal marine ecosystem. This study examines some apprehensions about the effectiveness of the existing legal system concerning prevention of coastal erosion. After examining several case studies in Scotland, the USA, and the Netherlands, this study proposes appropriate revisional legal measures that can be applied in Korea: first, the coastal management act should be revised for stronger, enforceable and practical legal grounds emphasizing minimal coastal erosion; second, the proposed "Comprehensive Coastal Erosion Prevention Plan" should be established and implemented in four steps such as characterization of issues through surveys of stakeholders and demand assessment, plan establishment, execution, and maintenance and management; third, there is a demand to establish and implement a legal framework to support monitoring activities which provide important data and information to prevent coastal erosion; fourth, the chronic region of damage is designated as the "Vulnerable Area" to be protected and managed accordingly; fifth, the "Coastal Coordination council" is established and operated for developing an integrated coastal management policy and visions for sustainable coastal zone, as well as coordinating and intervention of any activities which may cause coastal erosion.

Coastal erosion prevention by geotextile tube technology

Recently, geotextile tube technology has changed from being an alternative construction technique and, in fact, has advanced to become the prime solution of choice. This paper presents the various issues related to the geotextile tube technology and case history of shore protection at Young-Jin beach on the east coast of Korea. A stability analysis by the two-dimensional limit equilibrium theory is highlighted and the hydraulic model test results are described. Based on the results of stability analysis and hydraulic model tests, a double-lined geotextile tube installed with zero-water depth above crest was found to be the most stable and effective for wave absorption than other design plans. Also, the shoreline at Young-Jin beach was extended by about 2.4–7.6 m seaward, and seabed sand was gradually accumulated around areas covered by the geotextile tube.

Coastal modification due to human influence in south-western Taiwan

The coastal zone of southwest Taiwan is characterised by muddy tidal flats, offshore bars, spits, lagoons and coastal sand dunes. These geomorphic features from an essential part of the natural defences against sea-level change and coastal erosion. Between 1955 and 1995 the area bounded by the Pei-Kang and Tseng-Wen rivers underwent considerable land use and topographic changes. Two examples were studied using time-series aerial photographs, remote sensing images and geomorphological field mapping. The result of this investigation demonstrates the influence of human activities and the importance of the natural coastal landscape in acting as a first-line of coastal defence and protection in Taiwan. Attention is drawn to: (1) inappropriately designed or misplaced coastal engineering structures which may destroy or reduce the effectiveness of neighbouring natural and engineered structures leading to storm damage, flooding and encroachment by the sea; (2) the need for a co-ordinated coastal management program to regulate on-shore activities, in particular the removal of ground water within the coastal zone. This research demonstrates that there is significant land subsidence and inland penetration of sea water into the ground water system in the coastal zone. Human activities also lead to considerable financial expenditure on the prevention of coastal erosion in Taiwan.