(Fujian Geological Survey and Research Institute, Fuzhou 350003)

Coastal erosion and siltation are the main factors that change the coastal geological environment. Under the overall situation of global sea level rise, coastal erosion will become the most important natural disaster in the global coastal zone, and bay siltation will affect the sustainable development of port cities. It is a hot and difficult issue to reveal the profound changes of this geological environment and its objective influence on human living environment by monitoring means such as remote sensing technology and comparative analysis of time and space. On the basis of systematically summarizing the characteristics of modern coastal geology and geomorphology and the general situation of coastline changes since Holocene, this paper discusses the present situation and development trend of coastal changes in southern Fujian, and puts forward relevant environmental geological problems and prevention countermeasures.

Keywords: coastal changes; Coastal erosion; Gulf siltation; Environmental geology; southern Fujian

1 Features of modern coastal geology and geomorphology

The coastline of southern Fujian is generally distributed in NE-SW direction, and the coastline is tortuous, with a total length of about 1327.5km (including the island coastline of 347.8km), of which the artificial coastline is 450.0km, accounting for about 33.9% of the total coastline. The geological structure of this area is very complicated. The NNE and NE main faults control the distribution orientation of the coast, the NW extensional faults are combined with the former, and the bays, Hong Kong and Macao are developed. Coastal land landforms are mainly round low hills, red soil platforms and estuary plains. The coast is characterized by headlands alternating with bays, low mountains and plains. There are Jurassic-Cretaceous volcanic rocks, Yanshanian granites, Upper Triassic-Jurassic metamorphic rocks and Upper Tertiary basalts along the coast with strong weathering. Quaternary loose deposits in estuaries and harbors are relatively developed. According to the origin, morphology and anti-erosion ability of coastal lithology, the coasts in this area can be divided into three types: bedrock coast, sandy coast and muddy coast.

1. 1 bedrock coast

The bedrock coast is mainly distributed in Huian Chongwu, Jinjiang Weitou, Longhai Liuhui, Zhangpu Liu Ao, Gu Lei, Zhaoan Gongkou and other peninsula areas. In these areas, due to the strong erosion of seawater power and the erosion of shore current, marine erosion develops and there is almost no beach accumulation. According to the weathering degree and corrosion resistance, bedrock coast can be further divided into rock (fresh bedrock) coast and weathered crust coast.

1.2 sandy coast

Sandy coasts are mostly formed inside open bays between coastal hills or bedrock headlands, such as Huian Dagang, Jinjiang shenhu bay and Weitou Bay, Longhai Gangwei Bay and Longjiao Bay, Zhangpu Fu Tou Bay and Jiangjun Bay, Dongshan Wujiao Bay and Zhaoan Dacheng Bay. Coastal sandbars, sandbars and sand mouths, ocean terraces and plains are developed, and the coastline is relatively straight.

1.3 muddy coast

Muddy coast is mainly distributed at the top of wide bay and where rivers enter the sea. According to its material source and geographical location, it can be divided into harbor type and estuary type.

(1) Harbor types: mainly distributed in Meizhou Bay, Xiamen Port, Zhangpu Guzhen Bay, Dongshan Bay and Zhaoan Bay. The common characteristics of these harbors are: the land is surrounded by low hills or platforms, and there is often an island barrier at the mouth of the bay, and there is often a bay in the middle, which is semi-closed; Therefore, the wave action is weak, the bank slope is low and the beach is open. Its material mainly comes from the weathering crust of surrounding bedrock and is deposited by temporary surface water flow or coastal current, tidal current and waves. According to the field investigation, the harbor-type muddy coast in southern Fujian is still in the state of silting up.

(2) Estuary type: it is mainly distributed on both sides of the estuaries of larger rivers such as Jinjiang Estuary and Jiulong Estuary, and often forms a wide estuarine siltation plain. These plain fault basins were gradually backfilled and developed under the long-term external dynamic interaction between the Shui Gu estuary and the sea, with flat topography and single landform type, and most of them are in siltation at present.

There are scattered flaky mangroves in the tidal flat wetlands of harbors and estuaries. At present, the well-protected ones are mainly Dongshan Bay, Bamboo Pagoda at Zhangjiang Estuary and Caoputou at Jiulong Estuary. Mangroves can promote beach siltation, prevent wind and shore consolidation, and purify seawater. It is suggested that the management and protection of the existing mangrove coast should be strengthened, and artificial planting should be carried out in some eroded coastal areas to improve the geological and ecological environment of the coastal zone.

2. Overview of coastal changes since Holocene.

2. 1 Early Holocene (12000 ~ 8000 years ago)

The climate began to warm, and with the melting of the last Quaternary glacier in the world, the sea level continued to rise sharply. 1From 2000 to 9500 years ago, the coast was invaded again, and the average sea level was about-1 1.0m (the elevation of the Yellow Sea, the same below). The coastline is slightly eastward, about 8000a years ago, and the sea level fluctuates slightly.

2.2 Middle Holocene (8000 ~ 2500 years ago)

The climate continues to warm and the sea level fluctuates at a high level. About 7500 years ago, it was the biggest transgression in Holocene, and the sea level could reach 5.0 ~10.0 m. The sea water invaded inland along the river, and the coastline was located several kilometers to dozens of kilometers west of the current coastline. About 6000 years ago, due to the differential movement of neotectonic fault blocks, all coastal seawater withdrew, and the average low sea level was about-5.0m Then, about 5400 ~ 3 100 years later, the sea level began to rise again, and the high sea level was about 4.0m, which was stable for a long time. Peat beds and shell dikes are developed in the land-sea junction zone, and the ancient coastline is slightly westward than it is now. Since then, there has been a small-scale retrogression.

2.3 Late Holocene (2500 years ago)

This is the period of modern riverbed evolution and tidal flat development. Regional sea level is basically stable, but there are some ups and downs. The last regression occurred about 1400 ~ 700 years ago. It can be seen that although the Holocene was transgression, it did not rise linearly, but there were many sea level fluctuations and shoreline changes (table 1, figure 1). Historical records and test data show that most of the coastal plains in this area were formed in the past thousand years. Quanzhou Plain was gradually accumulated after the Ming Dynasty (1368). According to the surface 14C dating analysis of Shatou Farm, the Longhai Plain is about 600 years ago. Remains of primitive ancient forests have been found in intertidal zones of shenhu bay (1987), Qianhu Bay (1999), Maluan Bay, Dongshan (200 1), Hu Sha Bay and Shishi (2005), indicating that the sea level has been rising recently.

1 Holocene paleo-sea surface markers and 14C chronology along the southern coast of Fujian.

sequential

Figure 1 Schematic diagram of Holocene ancient coastal changes in southern Fujian coastal areas [6]

3. Analysis of the present situation and trend of coastal zone change

3. 1 sea level change

Coastal change is a comprehensive reflection of sea level and land rise and fall. In recent years, scientists all over the world have warned that the greenhouse effect caused by carbon dioxide and the extensive use of chlorofluorocarbons in industry lead to the destruction of the atmospheric ozone layer and global warming, and the seawater temperature and sea level are on the rise. According to the data published by the State Oceanic Administration and the long-term monitoring data of dozens of ocean observation stations and tide gauge stations in China, the seawater temperature and sea level in most coastal areas of China are on the rise. Especially since the 1960s, the global sea temperature has been rising gradually. In the past century, the sea level has risen by an average of 14.4cm, and the southeast coast of China has risen by an average of 1 1.5cm, which is equivalent to the annual average rising rate of 1. 15mm/a, and the coastal rise of Fujian is predicted. Among them, Xiamen has increased by 10.54cm in 30 years, with an average increase rate of 3.40 mm/a.

3.2 continental crustal changes

The background of continental crustal deformation in this area is mainly influenced by the collision between the Philippine plate and the Eurasian plate. Under the action of the NWW-oriented geostress field, the NW plate in the south section of the NE Zhenghe-Dabu deep fault shows a downward trend, while the SE plate shows an upward trend. Therefore, the overall characteristics of crustal deformation are from inland to coastal and from north to south. Due to the activity of faults, there are still some relatively declining areas in the NW-trending fault depression area, such as Zhangpu and Dongshan Bay. According to the observation of the seismological department, the crustal deformation amplitude in the north of Hui 'an and Jinjiang (with an interval of 8.55 years) is +30 ~+20 mm, and the rising rate is 3.51~1.71mm/a; The south of Zhangzhou and Xiamen is +25 ~+20 mm, and the rising rate is 2.92 ~1.71mm/a; But to Zhangpu and Dongshan, it is-10 ~-30 mm, and the decline rate is1.17 ~ 3.51mm/a. The evidence of obvious decline trend in Dongshan Bay area is as follows: the stone tablet carved on the bedrock in Chen Cheng Town in the south of Dongshan Island for ten thousand years has been buried by sea sand; The dampproof seawall built in Xipu, Chengguan in the 1960s has long been scrapped. According to fishermen in Aojiao Village, houses above the original high tide line can now be flooded to a height of about 1.0m; Fishermen in Dongshan County have been salvaging bricks and tiles, as well as the bones of large vertebrates such as deer and bears in brother island waters. The legend of Dongshan County "sinking into Tokyo" is recorded in the county annals, which reflects from another side that the ancients living in this area also felt the changes and vicissitudes of the coast.

3.3 coastline changes

The sea level rise in this area has different manifestations in different areas. Macroscopically, for the section where the crustal deformation is on the rise, because the rising speed of the crust is basically equal to the rising speed of the sea level, it is in a relatively static state, and the influence of sea level rise on this area is relatively weak; For the section where the crustal deformation shows a downward trend, the rate of crustal decline is basically equal to the rate of sea level rise, and the superposition of the two causes the rate of sea level rise to double, which can reach 4.0 ~ 10.0 mm/a, which significantly changes the coastline and poses a serious threat to coastal areas. Microscopically, because the coastal land fluctuation, sea level change, ocean and estuary are often intertwined, the north and south coastlines of the operation area are also different. According to the measured topographic map (1959 ~ 198 1 year) and remote sensing method (1986 ~ 2000), the coastline changes in southern Fujian coastal areas can be divided into three types: eroded coast, silted coast and stable (balanced) coast.

(1) Erosion coast: islands, peninsulas or headlands in the open sea, shores perpendicular to waves, windward faces of bays, etc. Can be directly eroded by wind waves and tides. The coastal erosion rate is not only related to the intensity of external dynamic geological processes, but also controlled by the lithology of coastal composition. The rocky coast has strong corrosion resistance and slow erosion speed, so it is not easy to detect its changes in a short time. Its shape is mostly steep cliffs or underwater rock beaches, which are mainly distributed in the northeast and south of islands and peninsulas, such as Dabazha, Zhenhai-Liuhuijiao and Aojiao of Dongshan Island in Chongwu Peninsula. Strong weathering-Weathered crust coast is relatively poor in corrosion resistance, and its shape is often steep or vertical. Due to the strong erosion of waves, it is constantly flattened, often forming accumulation beaches or sand banks, such as the bridge head of Shijing in Nan 'an and Gui 'anliao in Shenzhen.

Due to artificial reclamation or sand mining and other engineering activities, the erosion phenomenon of sandy coast is also more prominent. For example, in the area around Dongshitatou, Weitouwan, sandy beaches used to be slightly uplifted or basically stable; However, since 1956, the coastal Xiaowan estuary has been built for sea filling, a large number of artificial dredging, the sediment entering the sea has been interrupted, the material supply is insufficient, and the coast has been strongly eroded. In recent 20 years, coastal erosion is 20.0 ~ 80.0 m, high tide beach erosion is 0.50 ~ 1.0 m, coastal sand dikes are completely eroded, and revetment works such as stone dikes have been repeatedly damaged. See Table 2 for the change rate of zero-meter line of representative eroded coast in this area.

Table 2 Statistical Table of Change Rate of Zero Rice Noodles in Southern Fujian Coastal Areas

The total length of eroded coast in the whole region is about 445.0km, accounting for 33.52% of the total length of coastline, mainly distributed in strongly weathered-strongly weathered bedrock coast and sandy coast.

(2) Muddy coast: mainly distributed in Quanzhou Bay, An Harbor, Tongan Bay, Xiamen Port, Jiuzhen Bay, Dongshan Bay, Zhaoan Bay and ports. Harbor-type silting banks are mainly distributed on both sides of the peninsula and the southwest side of the island. Although no river carries a large amount of sediment into this kind of bay, due to the recent hydrodynamic conditions such as sea level rise, fast tide onset and slow ebb tide, the sediment brought by shore currents and waves will be accumulated due to the weakening of hydrodynamic forces, especially in the lower abdomen and gentle shore slopes. Those bays with rich material sources will gradually become land, and the zero-meter line will extend to estuaries and shallow seas. Estuary-type warping dam is rich in sediment sources, weak in hydrodynamic force, wide and flat in beach surface and fine in composition, and has a very favorable sedimentary environment. The sedimentation rate of neutral line can reach 10.0 ~ 100.0 m/year, and the accumulation rate is 5.0 ~ 30.0 cm/year. ..

In addition, coastal engineering activities such as land reclamation, blocking the bay and intercepting the river, repairing dikes and building gates objectively hinder the smooth flow of water, reduce the tidal intake and accelerate the siltation of the harbor. For example, from the mouth of Luoyang River in Quanzhou Bay 1972, sluice gates have been built on Luoyang Bridge. With the implementation of "May 1st" reclamation project, Dongwei reclamation project and Baishawei reclamation project, the tidal area in this area has decreased by more than 1: 3, resulting in slow channel velocity, massive sediment deposition, tidal flat rising and serious channel blockage. From 1969 to 2000, the total amount of the zero-meter line pushed to the waterway on both sides of Houzhu Port reached 780.0 meters, with an average of about 25. 16 meters/year ... See Table 3 for the outward movement of the zero-meter line on the silted coast in this area.

The accumulated silted coast in the whole region is about 560.0km, accounting for 42. 18% of the total coastline. Among them, the coastline in natural siltation state is 360.0km long, and the coastline promoted by coastal engineering is about 200.0km long, accounting for 35.75438+0% of the total length of silted coast.

(3) Stable (balanced) coast: refers to the long-term basic balance of the dynamic changes of coastal erosion and deposition; Or the coast was originally eroded, and now the coastline tends to be stable after taking engineering or biological protection measures. The bedrock stabilizes the coast and is generally distributed in the harbor with relatively hidden terrain; Sandy stable coast, mainly distributed in open beaches parallel or nearly parallel to the direction of wave action. For example, in southern shenhu bay, although the seasonal changes are obvious, there are local erosion and siltation phenomena; However, the offshore water depth is rapid, the material source is limited, the erosion and siltation dynamics are basically balanced all the year round, and the beach remains stable.

The cumulative stable coastline in this area is about 322.5km, accounting for 24.29% of the total coastline. Among them, the natural scouring and silting balance bank section is 72.5km long; After the engineering reinforcement measures are taken, the length of the balance bank of erosion and deposition is about 250.0km.

Statistical table of change rate of zero-meter line in muddy coast of southern Fujian.

4 environmental geological problems of coastal changes

4. 1 Coastal erosion endangers the safety of coastal residents and infrastructure.

Under the current global sea level rise, coastal erosion will become the most important natural disaster in the global coastal zone. With seawater intrusion, coastal erosion and erosion retreat, coastal roads, dikes, cables and other infrastructure are often destroyed, threatening the safety of coastal projects such as ports and docks, aggravating port siltation and affecting the economic development of coastal areas.

(1) Every year, strong typhoons land on the coast of Fujian, and external dynamic actions such as tsunami, wind and waves strongly erode the coast of Xiamen University, and hundreds of meters of coastal roads are destroyed; The submarine cable from Zhongzhai to Tongan was also broken; The red clay platform from Yingcuo to Aoguan has suffered from coastal erosion and soil cliff development for a long time, which has caused coastal collapse and landslide, loss of soil and water strength, and a large amount of sediment entering the sea, further aggravating the siltation problem in Xiamen Port.

(2) Coastal erosion often damages revetment works such as seawalls and windbreaks, resulting in seawater intrusion, engulfing a large area of fertile land, causing soil salinization and sandstorm activities, worsening the coastal geological and ecological environment, and seriously threatening the life and property safety of coastal residents. At Zeng Cuo An Village-Gangzaipu on the east coast of Xiamen Island, the 250-meter seawall was completely destroyed, and the revetment works between it and Baishibao were also seriously damaged, as was Qingjiao 1000-meter seawall. Dozens of hectares of fertile land, more than 1000 households and 10 factories in the seawall are in danger of seawater intrusion and immersion.

(3) Although there is no obvious erosion on the coast, the beach is continuously eroded and shrunk, which leads to the deformation, displacement and instability of the bank slope and affects the stability and safety of ports, docks and other projects. With the deepening of the construction of the economic zone on the west side of the Taiwan Strait, coastal engineering construction will continue to increase, and coastal erosion will become the main factor endangering coastal engineering construction. According to the experience of developed countries, the most effective way to protect coastal erosion at present is to feed on the beach, supplemented by engineering measures such as guiding embankment to promote siltation and covering the outer breakwater. Of course, these measures still depend on the characteristics of coastal geological environment, and artificial sand supplement can also be used.

4.2 Bay siltation affects the sustainable development of port cities.

Xiamen, Quanzhou and Zhangzhou are all coastal port industrial and trade cities, especially Quanzhou has a long history, and the rise and fall of regional economy is closely related to coastal changes.

(1) During the Song and Yuan Dynasties (960 ~ 1368), Quanzhou Port was once a world port and the starting point of the Maritime Silk Road, with more than 15000 ships at sea. Outer ports include the port behind the mouth of Luoyang River, Anping Port at the mouth of Daying River and Otxue Island Port in Quanzhou Bay. In the 29th year of Yuan Dynasty (A.D. 1292), an Italian traveler, Kyle Polo, was ordered by Kublai Khan, the emperor of Yuan Dynasty, to escort Princess Ke Keqing to marry Persia and set sail from Quanzhou Port. 1974 The wooden ocean-going ship of the Song Dynasty unearthed in Houzhu Port (now preserved in Quanzhou Ancient Ship Exhibition Hall) is a witness to the glorious history of Quanzhou Port. However, by the tenth year of Chenghua in the Ming Dynasty (A.D. 1474), Quanzhou, which had been established for more than 380 years from the Northern Song Dynasty to the Ming Dynasty, was moved to Fuzhou because of the port blockade, and Quanzhou also changed from the largest port city in China to a "historical and cultural city". With regard to the decline of Quanzhou Port, many commentators have focused on social factors, but the serious siltation of the port and the continuous extrapolation of the coastline are still ironclad facts. Zhangzhou Port Crossing (Haicheng) rose in the middle of Ming Dynasty, mainly replacing Quanzhou Port in decline. Businessmen once gathered here, foreign ships moored and towns were bustling; In the 15th year of Li Yong (A.D. 166 1), the national hero Zheng Chenggong rallied his troops here, reorganized his crusade, and recovered Taiwan Province in one fell swoop. However, the good times did not last long. With the siltation of the bay, shallow siltation of the waterway and the opening of Xiamen Port, a "five-port trading port", Zhangzhou Yuegang also declined.

(2) Port site selection should be based on the principles of stable coastline, water depth, less siltation, shelter from the wind in the port and small waves. From the perspective of coastal changes, the coastlines of Chongwu Peninsula, Shishi Xiangzhi, Jinjiang Shenhu, the northeast coast of Jinmen, the Great and Small Jinmen Strait, Zhangpu Liu Ao, Xiazhai and Dongshan Port are relatively stable and have the conditions for port construction. But as far as the current situation is concerned, it seems that some coastal sections can build ports; However, judging from the development trend of coastal changes, it is not appropriate to take effective measures to control them. For example, in Haicang-Yuqian section of Xiamen in Jiulong River Estuary, the siltation rate of north beach coastline is 12 1.0m/a, and that of the east side of Haimen Island is 105.0m/a, and the siltation rate is 2 1.0cm/a, which will continue to develop for 30-40 years. With the advancement of the zero-meter line, the bottom of the beach is gradually silted and the water depth becomes shallow, which is very unfavorable for port construction.

4.3 Tidal flat siltation brings new problems to aquaculture.

It is generally believed that beach siltation is beneficial to the development of aquaculture, but the beach accumulation rate in this area is greater than the sea level rise rate, so the coastal beach area is still expanding and the hydrodynamic conditions are also slowing down. The development of aquaculture should not only consider the development trend of tidal flat area, but also consider the pollution of tidal flat geological environment.

(1) Due to the continuous siltation of estuaries and bays, new sediments cover the old sediments every year, which leads to changes in the geological and ecological environment of benthos and plankton, making it difficult for some organisms to continue to adapt and reproduce, and the biodiversity is seriously threatened. For example, Tongan Bay in Xiamen, due to the construction of sluice at the estuary and the large-scale reclamation of Bingzhou and Dongkeng in the bay, the ebb tide velocity is greatly reduced and muddy sediments are rapidly deposited. The height ratio between the beach and the waterway is 2.0 ~ 5.0 cm/a, and the thickness of silt layer is 65,438+00 ~ 65,438+000 cm, which makes Xiamen amphioxus, a rare fish originally living here (made up of

(2) With the development of industrial and agricultural production, the discharge of "three wastes" is increasing, and the environmental pollution load is increasing. Pollutants brought by rivers or currents are often concentrated in places with weak hydrodynamic conditions at the top of estuaries and bays, resulting in lack of oxygen in water bodies or a sharp increase in the contents of harmful substances and elements in tidal flat siltation areas; This will change the geological and ecological environment of the original beach, make it difficult for aquatic organisms to survive or create a vicious circle, and then it is not suitable for aquaculture. This is a new problem that aquaculture has to face in the future and needs to be studied and solved.

5 concluding remarks

(1) The coastline of southern Fujian is long 1327.5km, and the coast is divided into three types: bedrock coast, sandy coast and muddy coast. Among them, bedrock coast is divided into rock coast and weathering crust coast; Muddy coast is divided into harbor type and estuary type. Coastal mangroves have the functions of promoting siltation, wind prevention, shore consolidation and seawater purification. It is suggested that management and protection should be strengthened, and artificial planting should be carried out in some eroded coastal areas to improve the eco-geological environment of coastal areas.

(2) Although the Holocene was transgression, there were many sea level fluctuations and shoreline changes. Historical records and test data show that most of the coastal plains in this area were formed in the past thousand years. Remains of primitive ancient forests have been found in intertidal zones of shenhu bay (1987), Qianhu Bay (1999), Maluan Bay, Dongshan (200 1), Hu Sha Bay and Shishi (2005), indicating that the sea level is still rising recently.

(3) Coastal change is a comprehensive reflection of sea level and land rise and fall. The coastal erosion in the whole region is 445.0km, accounting for 33.52% of the total coastline, mainly distributed in strongly weathered-strongly weathered bedrock coast and sandy coast; The accumulated silted coast is 560.0km, accounting for 42. 18% of the total coastline, mainly distributed in the muddy coast of estuaries and harbors. The total length of the stable (balanced) coastline is 322.5 kilometers, accounting for 24.29% of the total length of the coastline. Among them, the natural silting coastal area is 360.0km, and the engineering silting coastal area is 200.0km, accounting for 35.71%of the silting coastal area; The natural scouring and silting balance bank section is 72.5km, and the scouring and silting basically balance bank section is 250.0km after taking engineering reinforcement measures.

(4) Coastal erosion often damages coastal roads, dikes, cables and other infrastructure. , threatening the stability and safety of coastal projects such as ports and docks, aggravating port siltation and affecting the economic development of coastal areas. At present, the most effective method to protect coastal erosion is beach feeding, supplemented by engineering measures such as guiding embankment to promote siltation and covering outer breakwater, or artificial sand supplement method can be adopted.

(5) Xiamen, Quanzhou, Zhangzhou and other port cities, economic development is closely related to coastal changes. Port site selection should be based on the principles of stable coastline, water depth, less silt, shelter from the wind in the port and small waves. From the perspective of coastal changes, the coastlines of Chongwu Peninsula, Shishi Xiangzhi, Jinjiang Shenhu, the northeast coast of Jinmen, the Great and Small Jinmen Strait, Zhangpu Liu Ao, Xiazhai and Dongshan Port are relatively stable and have the conditions for port construction.

(6) The tidal flat accumulation rate in this area is greater than the sea level rise rate, so the coastal tidal flat area is still expanding and the hydrodynamic conditions are also slowing down. The development of aquaculture should not only consider the development trend of tidal flat area, but also consider the pollution of tidal flat geological environment.

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Environmental geological problems of coastline changes in southern Fujian

Jun Lin

(Fujian Geological Survey Institute, Fuzhou 350003)

Abstract: With the global sea level rising, coastal erosion is the main natural disaster and bay accumulation that affects the sustainable development of port cities. Therefore, coastal erosion and bay siltation are considered to be the main problems to be solved to improve the coastal geological environment. On the basis of summarizing the characteristics of modern coastal geography and coastline changes since Holocene, the present situation and development trend of coastline changes in southern Fujian are studied.

Keywords: coastal changes; Coastal erosion; Gulf gathering; Environmental geology; Southern Fujian coastal areas