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Analysis of Mechanism and Influencing Factors of Coastal Frosion in Fujian Province

Author: LiuJianHui
Tutor: CaiFeng;CaoLiHua
School: Ocean University of China
Course: Marine Geology
Keywords: Sandy coast in Fujian Soft sea cliffs Dune Artificial coastal landforms Coastal erosion
CLC: P737.1
Type: PhD thesis
Year: 2010
Downloads: 80
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Abstract


Coastal erosion, particularly the sandy coastal erosion has become one of today's Earth science research focus. Since the 1970s, the the Fujian coastal erosion situation is worsening, and currently about 60% of the sandy shoreline in retrogradation state. In this paper, the sandy coast of Fujian as the object of study, based on field survey data, combined with historical topographic maps, satellite images, and the first eight achievements, coastal landform type differences, from a different point of view of time and space to clarify the various types of coastal erosion process and mechanisms. Mainly in three areas of research: (1) Based on the Fujian coast a large number of field measurements and historical data, combined with nearly 50 years to three different periods (1961,1983,2004) topographic maps the digitized shoreline Information extracted contrast to the analysis of the spatial distribution of Fujian coastal erosion, including the scope of the distribution and location characteristics. And based on the quantitative analysis of shoreline retrogradation divided the the Fujian coastal erosion strength class then discusses the distribution of the underlying causes of the erosion intensity differences. (2) In view of the coastal landforms erosion processes and intensity control role, according to the results of field investigations Fujian sandy shores of the beach and near shore topography divided system of soft sea cliff beach dunes a beach system as well as artificial landforms the beach system the three basic landforms combination type, and to explore the three types of landforms erosion process. ● profile through periodic observation and monitoring of shoreline erosion explore the topography of the sea cliff - beach system change process. According to the analysis of the Yaan soil physical properties, of the moisture content of the soil on the sea cliff edge slope stability, and further discussion of the coupling of precipitation and ocean power sea cliff erosion process. Around based on the many dune - beach landforms cyclical measurement and storm tracking survey, analysis the dunes - Beach erosion and recovery process, and to explore the role of marine power and wind power in the recovery process, reveal the dunes - Beach erosion the main factors and analyzed the type coast storm under the geomorphological processes. ● instance of Dongshan Island, Majestic Bay, Hoi An Castle Peak Bay, and Chongwu Half Moon Bay explores the artificial revetment fishing harbor breakwater artificial landforms induced erosion adjacent to the sandy shores of the destruction process. (3) through field surveys and historical data, combined with the the Fujian coastal landforms environment background and history of the development of the coastal zone in recent years, based on specific analysis of many coast erosion mechanism, summarize the main factors of Fujian coastal erosion, comprehensive analysis of various factors in Fujian degree of coastal erosion process, and to investigate the contribution of the Typical Coast of different erosion factors. Article through the analysis, the study reached the following main conclusions: (1) the distribution of the erosion of the sandy coast of Fujian, in accordance with its strength can be divided into three main regions, northern Minjiang Estuary and southern Jiulong River Estuary is bounded Minjiang Estuary North Coast erosion intensity the lightest; south of Jiulong River Estuary erosion more serious; the Minjiang Estuary Jiulongjiang between the mouth central coast erosion is the most serious. The formation of new tectonic movement coastal tectonic framework, to control of a the Fujian coastal landforms substance obvious differences, creating a coastal erosion intensity distribution pattern. (2) soft sea cliffs Fujian coastal erosion is the most serious type of coast, and average annual retreat of the erosion rate of about 1.87m / a. The soft sea cliff erosion caused major external role battalion force for the infiltration of precipitation and ocean dynamic action, internal reason for the composition of the material resist ability weak. Rainfall Infiltration change the slope of the moisture content of the soil, causing the structural strength of the sea cliffs of soft soil decreases, generating landslide moved away from the coast then Yadi accumulation of the landslide substances in the wave, tidal and other marine dynamic action. The soft sea cliff retrogradation a loop iterative process, in accordance with the the camp force and the landscape changes can be attributed to its retrogradation process stabilization period action period, the period of destruction and removal of four stages. (3) the dunes - Beach erosion process can be grouped into two types: the erosion - the recovery dynamic equilibrium reversible process, major restoration force of marine power and wind, the former by the coast and to the shore sediment transport to supplement the beach surface sediment loss, the latter through the marsh surface sediment landward handling supplementary dune sediment loss; second is the irreversible process of the system long-term erosion of a beach, dunes retire irreversibility mainly due to the near shore, beach sand mining caused the persistent substances irreparable loss, the general performance of the beach face eclipse sand dune stabilization and dunes back the beach face erosion. (4) with respect to the natural process, human factors affect the performance of a diversified range of coastal erosion. Although artificial revetment fixed coastline the nearby beach storm response strength but strengthened, leading to the surface under the embankment before beach Beach erosion, slope steepening, sediment coarsening degradation. Will also result in a reduction in the downstream material input, causing downstream coastal erosion. The fishing harbor breakwater construction change neighborhood sediment balance and dynamic environment, often cause the breakwater upstream to the accumulation downstream side erosion. (5) Coastal erosion is the result of the interaction of many factors, different factors have different effects of spatial and temporal scales. Sea level rise and reduced sediment load into the sea in rivers is the Fujian coastal erosion important background factors control the overall erosion trends of the Fujian coast; Fujian coast frequent tropical storms often lead to strong short-cycle of the local coastal erosion and damage, but they often Fujian, southern widely distributed soft Yaan cause permanent erosion; coastal human activities on coastal erosion impact forms, nearshore sand mining causing loss Coast substances. strong erosion led directly to the coast, Fujian coastal erosion The common factor; unreasonable coastal engineering often will destroy the balance of coastal sediments, change Coast hydrodynamic environment, led to the partial erosion of the beach degradation and the adjacent coast.

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CLC: > Astronomy,Earth Sciences > Oceanography > Marine basic science > Marine geomorphology > Coastal landforms
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