Procedia Environmental Sciences 10 ( 2011 ) 1680 – 1684

doi: 10.1016/j.proenv.2011.09.264

Available online at www.sciencedirect.com

Conference Title

The Distributed Characteristics and Controlling Factors of the Formation of Coastal Wetlands in Tangshan

GAO Lian-feng1,2,3,, ZHANG Ying1,3, ZHANG Zhen-guo3

WANG Ying-Chun1,3, and ZHANG Peng1,3 1. College of Mining Engineering, Hebei United University, Tangshan, China..

2.College of Mining Engineering, Taiyuan University of Technology, Taiyuan China. 3. Key Laboratory Mineral Development and Security Technology of Hebei Province, Tangshan, China.

gaoxianlin@yeah.net

Abstract

Coastal wetlands are important land resources in Tangshan, including natural wetlands and artificial wetlands. Spatial form of wetlands is zonal distribution, contours approximately paralleling with the coastlines. The formation is controlled by the favorable weather conditions and good hydrogeological conditions, such as the rapid subsidence of ground caused by Neotectonics, abundant precipitation system and dense surface water. The formation and development of coastal wetlands in Tangshan is the response record to research coupling relationship among neotectonic movement - climate evolution - environmental changes.

Key Words: Tangshan, coastal wetlands, distributed characteristics, formation, controlling factors, neotectonic

1. Introduction

Coastal wetlands are lying between the terrestrial and marine ecosystems, which is the most biologically diverse, the most productive and the most valuable wetland ecosystems[1~4]. It has an irreplaceable role in resisting the flood, regulates runoff, flood and drought, degradation, pollution, climate regulation, control of coastal erosion, siltation land reclamation, landscaping, and has great ecological, economic and social value[5~9]. In recent years, with the large-scale construction in Caofeidian Scientific Development Demonstration Area (CSDDA), the development, use and dependence of coastal wetlands in Tangshan continue to be strengthened, how to protect and make rational use of this valuable resource has become an unavoidable reality problem.

2011 3rd International Conference on Environmental Science and Information Application Technology (ESIAT 2011)

1878-0296 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Conference ESIAT2011 Organization Committee.

© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of Conference ESIAT2011 Organization Committee.

Open access under CC BY-NC-ND license.

Open access under CC BY-NC-ND license.

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2. Distribution Characteristics and Types of Coastal Wetlands in Tangshan

Tangshan is located in the west bank of Bohai, the north of Yanshan, lying from north to south, and tilting from northwest to southeast. The landforms from land to sea are the low mountains, hills terrace, alluvial fan, sloping plain alluvial fan, alluvial, lacustrine plains, sea product, alluvial plain and delta. Coastline is 196.5km. There are 70 big and small islands, and the island coastline is 125.7km. The land coastline is between the Luanhe Mouth and Douhe River[10].

In general, the southeastern region is low and flat, and rainfall is more abundant in summer. Different sizes of the water originated from the Yanshan Mountains immit into the Bohai Sea. The sea and land along river deltas and coastline interact and develop rich wetland ecosystems. The main part of the wetland is the zonal distribution basically in accordance with paralleling contours and coastline approximately, which can be divided into the coastal plain, inter-tidal mudflats and low tide less than 6m. (Shown in Figure 1) Paddy fields area of Coastal plain is 36533ha, intertidal mudflat area is 82913ha, and shallow isobaths area less than 6m at low tide is 416800ha. Considered by the natural attributes of wetlands, Tangshan coastal wetlands can be divided into coastal beach, rivers, reed marshes and other natural wetlands, and paddy fields, salt fields, ponds, reservoirs, canals and other artificial wetlands[11~13].

Fig. 1 The sketch of Tangshan coastal wetland

The "wetland" in the research means the same geological origin, the land outside the part shallow water less than 6m at low tide, including natural wetlands dominated by the reed swamp and artificial wetlands dominated by salt, rice, the pools with fish, shrimp and crab (Shown in Table 1).

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3. The geological background of coastal wetlands in Tangshan In the tectonic position, Tangshan is located in the core parts of the Bohai Bay Basin. In the Cenozoic, due to the subduction of the Pacific plate, the sustainable settlement in the center of Bohai region is formed. Sea oil and gas exploration shows that in the Cenozoic basin the depth of the largest settlement is more than 10,000 meters[14~16]. In the Late Cenozoic, new tectonic movements are active, but settlement is still the main action. In Quaternary, affected by frequent climate fluctuations and transgression, characteristics of land and sea interactions are obvious. Continental alluvial plain, alluvial and lacustrine deposits are developed, and are overwhelmed by the sea many times with different thickness of intertidal sand and silt layer phase. Located in the "shoot under the nine rivers ", through the deposition and filling of the Yanshan River, the formation and development of wetlands has been laid a good foundation.As the study area is low and flat, the process of the plains has interaction with fluvial-lacustrine deposition and marine sediments. For Dawu Village in the southwestern study area, a few meters thick oyster reefs under 2~3m of surface sediment layer may be formed in the Holocene high sea level period (5800~7200a B.P.)[17]. The current distance from Dawu Village to The coast line is nearly 30km. a number of oyster reefs almost parallel to the current coast with altitude of 4~6m, clearly showed the characteristics of the coast of regression. Comprehensive study of sedimentary facies and depositional environments revealed that in Quaternary deposition rate of the coastal area in Tangshan reached 100~300m/Ma. Ebb Bay swamp reached 400~500m. the East Huangtuo swamps reached 800m. Under the joint action of the ongoing settlement river rapid filling, the study area experienced shallow lagoon

lake tidal depression, ultimately by river alluvium filling into the land, the distribution patterns lakes, swamps, tidal wetlands are formed.

Table 1 The types and distribution of the coastal wetlands in Tangshan

Types of wetlands

The name of wetlands

The range of wetlands Area of wetlands

(ha)

Altitude m

Types of sediment

Natural

wetlands

East Huang Tuo Swamp

39°07 ~39°19 N 118°23 ~118°28 E

1801 4 Silty clay

Luo chao wan Swamp

39°10 01 ~39°14 06 N 118°15 01 ~118°18 41 E

1792 1~5 Silty clay

Douhe Swamp 39°11 ~39°26 N 118°03 ~118°14 E

1876 1~4 Silty clay

Cao zhuang zi Swamp

39°11 55 ~39°14 34 N 118°43 00 ~118°47 09 E

1462 2~5 Silty clay

Shuohe Swamp 39°15 ~39°09 N 118°30 ~118°41 19 E

5120 2 Silty clay

Oil Gourd Park Swamp

39°29 ~39°34 N 117°55 ~118°01 E

4100 2~3 Silt clay

Artificial

wetlands

Salt field, aquaculture area

High tide line extending to the mainland about 10km or so 1

73750 0~3 Salt marsh soil

Freshwater aquaculture, reed swamp

extending from (1) to further land about 5km (2)

21680 2~3 Silt clay

Rice growing areas

extending from (2) to further land 5 ~ 10km

59810 3~7 Silt clay

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4. The controlling factors of the coastal wetlands formation in Tangshan

4.1 The controlling of the new tectonic movement

New tectonic movement has an important effect on geography, which restricts the basic topographic structure changes. Through the topography changes, water distribution and other elements of geographical environment changes are prompted, the formation of wetlands laid the basis of geological features, and the formation of wetlands, the rise and fall and evolution are controlled.

Caused by the Yanshan movement, the pattern, which is the northern uplift and the southern with tectonic subsidence, laid the basic framework and formed the sedimentary basin centered by Bohai Sea settlement. Intense activity of the Neotectonics resulted the earth was broken crust, breaking developed, a number of NEE and NWW faults intersected in Tangshan, and the most are Holocene active faults with earthquake-prone and sedimentary active[18~20]. Quaternary experienced 4 times episodic tectonic movements, resulting 4 distinct sections in the deposition region, from top to bottom which are Holocene~upper Pleistocene discontinuity(10~8ka B.P.), Upper Pleistocene and middle~lower discontinuity (50~40ka B.P.),Upper Pleistocene and middle Pleistocene discontinuity (100~80ka B.P.), middle Pleistocene and lower Pleistocene discontinuity (700~400ka B.P.)[21~24]. A great deal of oil exploration data (seismic and drilling) revealed (by far surpass normal) sedimentary thickness is about 50~1000m in the region from Late Pleistocene to Holocene. In the last century modern sedimentation rate is about 0.1cm/a for marsh wetland, about 0.5cm/a for salt marsh lagoon, and about 1.3~3cm a for open tidal flat[25,26]. Study area is controlled by new tectonic movement, resulted with topographic inequality and ups and downs of time. Wetlands have also experienced the complex formation and evolution.

4.2 The constraints of climatic conditions on the formation of wetlands

Wetland formation and development and space-time evolution are the response to global climate change. Climate change impacts on the wetlands. First it changes in temperature and precipitation, and then changes the hydrological cycle system of wetlands. Specific Hydrological conditions are the driving forces of formation and maintenance of wetland, small changes in hydrological characteristics lead to changes in wetland ecosystems. Therefore, the formation and evolution of wetlands are largely controlled by the climate change or even human activities.

The Asia inland arid in late Cenozoic and the occurrence of Quaternary glaciations have significant impact on the climate evolution in the study area. Study area belongs to warm temperate semi-humid continental monsoon climate with the characteristics of dry winter, wet summer, precipitation concentration, four distinct seasons and so on. The precipitation is abundant, mainly concentrated in July and August. The annual average rainfall is 620 to 750 mm, seasonal variation in rainfall is great and unevenly distributed. However, with the pace of global warming, in North China, the trend of climate warming and drying in recent years become increasingly intensified, resulting in reduced surface runoff, water table declining, shrinking wetlands, reduced function of the ecological environment. The reduced Wetland area and decreasing the water level were consistent with climate change. According to incomplete statistics, wetlands area (excluding the shallow water wetlands) has been reduced from 174667 ha in 1987 to 163682 ha in 2004.

4.3 The constraints of hydrogeological conditions on the formation of wetlands

Tangshan coastal wetland was developed in the transition zone of the marine, freshwater, terrestrial environment. The hydrological conditions of surface runoff, groundwater flow, waves, tides, precipitation and evaporation play direct influence on the formation, development, evolution of wetland. Hydrological conditions are the most sensitive factors for the wetland ecosystem, and hydrological conditions control the evolution of the wetland. In the late Quaternary, the transgression and regression caused by sea level changes have significant effects on the formation and development of wetlands in the study area. In a shorter time scale, surface runoff recharge, precipitation and evaporation are the major constraints on

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wetlands development in study area. There are many rivers in the region. The different sizes of rivers originated from Yanshan Mountains are more than 70. The basin areas over 200km2 have 16 rivers, represented by Luan River, the Dragon River, Douhe, Jiyun River. These rivers run to the south into the sea, and the average runoff volume of wetlands for many years is 1.89×108m3, which provide sufficient water supply conditions for the formation of coastal wetlands. The sediment types include silt clay and silty clay with thick layers. The types could effectively prevent the infiltration of surface water, providing favorable conditions for the formation of coastal wetlands in Tangshan.

5. Conclusions

The formation and distribution of wetlands are the results of new tectonics, Quaternary topography and landscape, monsoon activity, climate evolution, river basins and other factors in short geological time scales. The formation and development of coastal wetland in Tangshan are the response record of tectonic movement - climate evolution - coupling relationship between environmental changes in study area.

Acknowledgements

This research was supported by Education Department of Hebei Province (Z2009121, 2009443, 2010248) and National Natural Science Foundation of China (No:40972079).

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