EVALUATION OF EROSION PRODUCTIVITY IMPACT CALCULATOR （EPIC） MODEL FOR MIDDLE MOUNTAIN REGION OF NEPAL

This study verifies the applicability of EPIC model for an erosion plot (61 .2 m~2) and an uplandterraced watershed (72 ha) using a total of 94 rainfall events over a study period of two years. Inorder to analyze the effect of storm size on runoff and soil loss processes, rainfall events aredivided into three groups: small (<25mm), moderate (25--50mm) and large (>50mm). Resultsindicate that the model could predict reasonably well the runoff and soil loss from the erosion plotand the watershed for the moderate and large rainfall events. However, the runoff and soil lossprediction for the small rainfall events is found to be poor. On annual basis, both surface runoff andsoil loss predictions match well the observations. In ligh of the importance of the moderate andlarge rainfall events in producing most of the annual runoff and soil loss in the study area, the EPICmodel is applied to assess the impacts of erosion on agricultural productivity and to evaluatemanagement practices to protect watersheds in the     

SEDIMENT CONTROL MEASURES IN SERIOUS SOIL EROSION REGION IN CHINA

I.INTRODUCTIONSoilerosionareasinChinasearchto3.67millionkm'whichoccupies38.2%OfthewholeareainChina.Thesoilerosionregionisspreadingovertheti)holecountry.Amongthat,soilerosionbyrainfallistermedas"watererosion"whichisdistributedinmountainsandhillarea.soilerosionbywindistermedas"winderosion",mainlydistributedinareasalongtheGreatWall,soilerosionbyfreezeandmeltistermedas"freezeerosion",mainlydistributedinhighmountainarea.Inthepastfortyyears,manyintegrateharnessmeasureshavebeenaPPliedindiffer…     

DEVELOPMENT OF SOIL EROSION INDEX MODEL IN TAIWAN WATERSHEDS

1 INTRODUCTIONSoil erosion of land surface caused by over development has become more and more serious.Environmental damage resulted from accelerated soil erosion has attracted much attention especi ally overthe past 20 years. Soil erosion stUdies have focused primarily on soil characteristics and climaticvariations. Great achievements have been made in understanding the mechanism of soil erosion, whichallows the develoPment of evaluation models for all types of soil erosion problems. Th…     

SOIL EROSION PROCESS RESEARCH AND ITS POTENTIAL IMPACT ON EROSION PREDICTION MODEL DEVELOPMENT

During the past 50 years, many research efforts have been invested in understanding soil erosion process and development of erosion prediction models at various scales. This paper briefly introduces the erosion process and prediction model development in the USA. Especially, this paper focuses on discussing potential impacts of the erosion process on erosion model development, and future directions of the soil erosion process research and process- based model development. 1 DEVELOPMENT O…     

ANALYSIS OF SOIL EROSION CHARACTERISTICS AND SEDIMENT SOURCES FOR THE YANTZE THREE GORGES REGION

In this paper the researches made in 1981-1990 have identified that the annual soil loss in the Three Gorges region is 157 million t. and the annual incoming sediment load of the Three Gorges reservoir is 40 million t. Soil erosion increases with the destruction of vegetative cover and its subsequent evolution. The annual amounts of sediment erosion for forest land, shrub land, grassland and farmland make up respectively 6.19%, 10.76%, 23.05% and 60% of the total erosion of the Three Gorges region; the quantities of incoming sediment load to the Yangtze River from the above four types of land account for 5.95%, 12.42%, 35.46% and 46.1 % of the total amount of sediment transported to the reservoir. The farmland of offers the main source of sediment. Gravitational erosion produces more bed loads, which will present serious threat to the Three Gorges Project if entering the reservoir. Resettlement of people to the upper parts of the mountainous areas for agricultural production will increase the sediment yield of the Three Gorges region by 10-20 million t and increase the incoming sediment of the Yangtze River by 50-60 million t. Consequently, it is necessary to make a realistic assessment of the soil erosion in the Three Gorges region.     

STUDY ON THE DYNAMIC PROCESS OF RILL EROSION OF LOESS SLOPE SURFACE

1 mTRODUCTIONAs a woridwide concem, excessive water erosion induces land degradation, causes losses of plantnutrients, and Ieads to off site enVironmental problems such as sedimentahon streams and reservoirs. mllerosion, which results from concentraed flow in a lindted and confined space, plays imPortant roles inthe erosion systCm on uPland areas. Data listed in Table l show its contribution and imPoftance to thetOtal slope soil losses. In the last decades, stodies on the physical mecha…     

CONTRIBUTIONS OF TUNNEL EROSION TO SEDIMENT YIELD IN A SEMI-ARID BASIN IN THE LOESS PLATEAU OF CHINA

1 INTRODUCTIONSubsurface erosion has been increasingly recognized as a significant hillslope geomorphologic process(Carson and ~y, 1972; McCaig, 1983;, Harvey, 1982;Bryan and Harvey, 1985; Crouch andMcGarrity, 1986; Walsh and Howeds, 1988). However, most of the studies were conducted in hubedareas, especially in Britain (e.g. Gilman and Newson, 1980; Jones, 1981; Wilson and Small, 1984; Jones,1987; Jones et al, 1997). Jones and Crane (1984) found that soil piping contributes about …     

EFFECTS OF WATERSHED MANAGEMENT ON THE REDUCTION OF SEDIMENT AND RUNOFF IN THE JIALING RIVER,CHINA

The Three Gorges Project is one of the largest hydro-projects in the world and has drawn many debates inside China and abroad. The major concern is that sediment load from the river basin may eventually fail the functions of the project for flood control and power generation. To reduce sedimentation in the reservoir, watershed management has been adopted. However, there is limited information regarding the effectiveness of various control measures such as terracing and afforestation on a watershed scale. The Jialing River, a main tributary of the Yangtze River, contributes approximately 25% of the total sediment load in the main river but only represents 8% of the whole basin area. There have been various land use patterns and extensive human activities for thousands of years in the Jialing River watershed. Based on analysis of the major factors affecting erosion in the Jialing River watershed, the main watershed management strategies (afforestation, farming and engineering practice) are illustrated, and their effects on the reduction of sediment and runoff are studied in detail. The sediment budget of the watershed shows that 1/3 of the sediment yield is trapped by the erosion control measures (afforestation and farming) on the slope, 1/3 is trapped by the reservoirs, ponds and dams within the watershed, and only about 1/3 is transported into the Yangtze River, which will affect the Three Gorges Project.     

DEFORESTATION-A CAUSE FOR THE ECOLOGICAL DISASTER OF SOIL EROSION IN IMO STATE,SE NIGERIA

1　ＩＮＴＲＯＤＵＣＴＩＯＮ　Ｓｏｉｌｅｒｏｓｉｏｎｉｓａｎａｔｕｒａｌｐｒｏｃｅｓｓｗｈｉｃｈｈａｓｂｅｅｎｉｎｏｐｅｒａｔｉｏｎｓｉｎｃｅｔｈｅｆｏｒｍａｔｉｏｎｏｆｔｈｅｅａｒｔｈ.Ｓｏｉｌｅｒｏｓｉｏｎｉｎｃｌｕｄｅｓｂｏｔｈｔｈｅｐｒｏｃｅｓ...     

ESTIMATION OF SOIL EROSION IN A RESERVOIR WATERSHED USING ^137CS FALLOUT RADIONUCLIDE

Sedimentation from soil erosion is a critical reservoir watershed management issue. Due to the difficulty of field investigations, empirical formulas are commonly used to estimate the soil erosion rate. However, these estimations are often far from accurate. An effective alternative to estimating soil erosion is to analyze the spatial variation of 137Cs inventory in the soil. 137Cs can be adsorbed by the soil and is widely assumed to change its distribution only when disturbed by rainfall and human activities. Thus, 137Cs distributed in soils can be a useful environmental tracer to estimate soil erosion. In this study, the net soil loss estimate is 108,346 t/yr and the gross erosion and net erosion rates are 10.1 and 9 t/ha yr respectively. The sediment delivery ratio is therefore estimated to be 0.9 based on the two erosion rates. Because of the steep hillsides in the watershed, only 10% of the sediment yield stayed in the deposition sites and 90% was transported to the river as the sediment output. Soil erosion estimates from spatial variations of the 137Cs activity in the Baishi river watershed showed satisfactory accuracy when compared to sediment yield data. Using soil 137Cs concentrations is therefore a feasible method for estimating soil loss or deposition in Taiwan. Data sampling, analysis and result of this approach are given in this paper.     

DEVELOPMENT OF A SURFACE PLUME MODEL AND ITS APPLICATION TO SEDIMENT TRANSPORT MODELLING OF DREDGING IN COASTAL WATERS

I INTRODUCTIONSediment dredging operations are effective means of maintaining the natural navigation channel ofshipping for transportation of passengers and cargoes (Goldbeck 1998, Wakeman 1998). Expansions ofexisting ports to facilitate the groWth in marine traffic often necessitate navigation channel dredgingactivities (Foxworthy et. al. 1995, Luger et. al. 1998). Dredging is also heavily used for marine mining ofthe scabed deposits for gold or minerals (Anon 1996, Gamett 1996), and …     

祁连山中段现代应力活动与浅层应力预报地震研究

本文在研究全新世断层活动的基础上，运用构造解析、水系应力场等多种方法，对祁连山中段的现代应力活动状态进行了综合研究，其结论是：区域主压应力方向为北东－南西向，平均Ｎ５０°Ｅ；但在大区范围内显示了应力场的空间变化，局部地区随时间亦有动态变化。此外，还结合祁连站的观测资料，研究了中强震和应变曲线的对应关系，并取得了较好的预报效果。     

MT重复测量在地震中短期预报中的应用──祁连山中段MT剖面监测研究

本文研究了青藏高原北缘第一个长约４００ｋｍ的ＭＴ监测剖面上所获得的５次５－７级地震前后的资料。着重分析了在相当于大陆多震层深度范围内壳内介质的多种ＭＴ参数（视电阻率、相位、主轴方位角、扭曲度等）．这些ＭＴ参数在大范围内的同步－同相变化和局部区域之间的超前、滞后变化、相对变化幅度随震中距增大而衰减的特征，可能分别对应着构造孕育型大震的地区性场兆和构造运动型强震的区域性场兆，形成了地震活动大背景叠加小背景的一种链式关系。运用＂ＭＴ监测优显参数＂进行择优监测，将可能为大陆地震的震源物理发展过程和中短期预报提供丰富可靠的判据。     

利用长周期面波研究华北地区地壳与上地幔结构的横向非均匀性

本文以太行山为界将华北地区分为东西两部分,东部为河淮块体,西部为鄂尔多斯块体.利用最小二乘法,从混合路径基阶瑞利面波群速度频散提取两块体的纯路径频散,并反演其地壳、上地幔的层状结构.所得结表果明,两块体的面波频散和地壳、上地幔结构存在明显差异.东部的河淮块体地壳较薄,地壳内平均速度比西部的鄂尔多斯块体壳内平均速度约低0.13km/s,壳内20km深度左右出现低速层;而西部的块体壳内速度成层递增,未见低速层出现.两块体上地幔顶部速度均偏低,地幔低速层的埋藏深度基本相同.但西部块体地幔低速层厚,且比东部块体地幔低速层的速度约低0.3km/s.     

利用长周期面波研究华北地区地壳与上地幔结构的横向非均匀性

本文以太行山为界将华北地区分为东西两部分,东部为河淮块体,西部为鄂尔多斯块体.利用最小二乘法,从混合路径基阶瑞利面波群速度频散提取两块体的纯路径频散,并反演其地壳、上地幔的层状结构.所得结表果明,两块体的面波频散和地壳、上地幔结构存在明显差异.东部的河淮块体地壳较薄,地壳内平均速度比西部的鄂尔多斯块体壳内平均速度约低0.13km/s,壳内20km深度左右出现低速层;而西部的块体壳内速度成层递增,未见低速层出现.两块体上地幔顶部速度均偏低,地幔低速层的埋藏深度基本相同.但西部块体地幔低速层厚,且比东部块体地幔低速层的速度约低0.3km/s.     

利用长周期面波研究华北地区地壳与上地幔结构的横向非均匀性

本文以太行山为界将华北地区分为东西两部分,东部为河淮块体,西部为鄂尔多斯块体.利用最小二乘法,从混合路径基阶瑞利面波群速度频散提取两块体的纯路径频散,并反演其地壳、上地幔的层状结构.所得结表果明,两块体的面波频散和地壳、上地幔结构存在明显差异.东部的河淮块体地壳较薄,地壳内平均速度比西部的鄂尔多斯块体壳内平均速度约低0.13km/s,壳内20km深度左右出现低速层;而西部的块体壳内速度成层递增,未见低速层出现.两块体上地幔顶部速度均偏低,地幔低速层的埋藏深度基本相同.但西部块体地幔低速层厚,且比东部块体地幔低速层的速度约低0.3km/s.