Study On Soil Erosion's Effect By Rural Settlement And Its Protecting Strategies In The More Sediment And Coarse Sediment Region Of Northern Shaanxi

More sediment and coarse sediment Region in Northern Shaanxi is the area of the north of Yan'an or Yan River in Shaanxi province. The area is 43,500km~2 large, which accounts for 58% of all More sediment and coarse sediment Region. The area produces 180 million tons coarse sand one year, which accounts for 43.48% of lower reaches of Huanghe River. It causes Huanghe River driving up every year, and it is the main origin of bedload in Huanghe River. Serious soil erosion of the area is the results of flimsy entironment and strong human activity. Thereinto cave-house no doubt is one of important artificial factors. Important academic value and actual meaning are available in researching on soil erosion of cave-house and countercheck , also in enriching the content of soil erosion knowledge, establish countermeasure of reducing bedload in Huanghe River and promote regional economic persisting development.Semiorientational observation and field survey measure are adopted in the study, for the first time the following were researched, the meaning and formative process of soil erosion of cave-house, effecting factors, estimating index, soil erosion effect, fluctuant attenuation were reshaped also including soil erosion prevention and construction of ecological village and country. The abstract as follows:1 , Search actuality and development of soil erosion are summarized in the paper. The former research in soil erosion laid particular stress on given nature condition. Accoding to standpoint of being based on man and persisting development, soil erosion of production and measure of improving in habitation are one of main direction of soil erosion development in future.2, The style, distributing, model and characteristic of cave-house of the area are systemically analyzed, the paper also brings forward reconstituting geographical sorting system. The style and model are clearly considered distributing along channel and slope. Its construction must plane the slope and the digging may disturb loess hill, slope and stratum . The peak of cave-house, courtyard, byroad , space between house, and damaged cliff, heaped man-made slope, the disused and collapsed cave-house are formed in this process.3, For the first time, the meaning, formative process and effect factor are researched. A new erosion circumstance is caused after the cave-house destroyed ground condition and changed the ground, therefore soil erosion is more serious. Besides the familiar erosion modes, collapsing in the disused cave-house and heaped-slope disuniform-sink are also available .Besides the natural factors, the more important factors are artificial factors, the characters of which are totally different from soil erosion of natural slope, destroying woods and opening up wasteland and culturing on slope.4, For the first time, estimation system for soil erosion of cave-house is researched. According to dispersing distribution of soil erosion of cave-house and describing the linear or punctate erosion, three evaluation indices are brought forward.5 , For the first time, the representative the cave-house in the area and the effect data of the soil erosion of re-shape land are researched. The result as follows: R is 4.59t/p.a, â–³R is 2.96 t/p.a, most part is caused by the cave-house collapsing (R8=â–³ R8=3.20t/p.a) , which accounts for 69.72% of all erosion. If cave-house collapsing is not considered, the R of normal cave-house is 1.39 t/p.a, AR is 0.25 t/p.a . The result indicates that R is 51,100 t/a, r is 4.02%, and settlement area is 1.86% of all area in the area of Jiuyuangou of Suide county and R is 62,700 t/a, r is 6.09%, settlement area is 1.03% of all area in the area of Qingyanggou of Yuyan county. It shows the soil erosion in cave-house cannot be ignored.6, For the first time, the change characteristic of the soil erosion of the cave-house is researched. The conclude shows that the attenuation of the soil erosion of the cave-house is a two-peak structure from built to collapsed. The factor of the soil erosion is very clear in the building year, which is 2.09 t/p.a, AR is 0.45 t/p.a, this is the first peak, then it attenuated. The factor of the 20 years soil erosion is 0.88 t/p.a, A R is 0.75 t/p.a. It reduced 1.21 t/p.a from the building year, k1 is 0.06 t/p.a in the all living period (1-20 years). The disused and collapsed cave-house caused the second peak, it loses 53.42 t/k.a per hole per year, and 3.20 t/p.a per man per year, it is 69.72% of all erosion, and also is new increased. The rate of the soil erosion attenuation, k2, which is reflected by the losing coefficient in different losing periods is 0.0644.7, The six principles are put forward in soil erosion of the cave-house. The five systems should be builded. The education and concept should be set up for constructing ecological town, constructing the representative should be the...