Terrace Design And Earthwork Calculation Optimization In Hilly Areas Based On Spatial Analysis Methods

To deal with the sloping lands in the Southwest China hilly areas,the construction of terraces can be changed into the slope of the terrain,so as to prevent the soil erosion and increase the soil moisture effectively.It is also an important land remediation measure to increase the agricultural production and improve the ecological environment from the regional areas.Cutting down the slope from sloping cropland and building terrace are related to soil and water conservation abiding with the improvement of farming condition in hilly areas.However,the researches about land leveling in downland and upland have always been considered as the difficult sections in land reclamation.The reason is that terrain of southwest hilly regions is particularly sophisticated.In addition,the distribution of farmlands is fairly fragmentized.There is also the most prominent karst distribution in our country.So that,the process of soil formation of arable land is slow and the soil layer is thin,what's more,the area with thicker soil layer does not exceed 1 m,which makes it difficult to control.As far as the hilly area of Chongqing is concerned,a large number of cultivated land slopes are distributed from 15 to 25 gradients,which is a conditional construction area of the horizontal terraces.At present,the research on the land leveling design in conditional construction area is relatively insufficient.In the actual operation process,terrace field division is mainly based on manual experience and comprehensive rules,lacking of the objective method guidance,which affects the calculation accuracy of the land leveling earthwork quantity.Therefore,it is necessary to conduct in-depth study on the design of land leveling plots and earthwork calculation of Sloping Farmland in this area,which has important scientific significance for fully recognizing regional characteristics and effectively controlling the budget of land consolidation projects.In this paper,based on the examples of slope farmland consolidation in recent years and relevant policy documents,the slope farmland in Dinjiang County of Chongqing City is selected as the research object.On the lack of large-scale topographic maps as basic dataset,this article used a status land use map as a data source that the scale is one centimeter to the two kilometers,which a digital elevation model was created by the data source.Dry sloping lands which the slope degree from 20 to 25 gradients,were chosen to be used as land leveling experiment object.In order to analyze and estimate the field elevation difference?field width and earth volume for the designed terraces,Equal Interval classification,Quantile classification,Geometrical Interval classification and Natural Breaks classification were used to test terraces classified methods.At the end of this article,there was an descriptive analysis imitating the transformation of earthwork between average field elevation difference and field.The conclusions of the thesis are as the follows,Firstly,I have achieved the overall balance of the land leveling and excavation work in the testarea by taking the average elevation of each field as the design elevation for terraces.Moreover,I have constructed its spatial model of the flattened planning area by high-resolution DEM,based on the spatial analysis function in ArcGIS software.For the hilly and mountainous areas in southwest China where the topographic influence is great,the land leveling design to achieve the balance of excavation and filling can further reduce the cost of earthwork transportation in actual construction.Secondly,by comparing the factors of flattened fields,it can be seen that with the increase of the number of plots divided,the elevation difference,average width and earthwork volume of the fields gradually decrease,but the reduction gradually slows down.For the purpose of maintain the identical proportion,the field elevation difference at the top of the mountain which from outcomes of Quantile classification is excessively high.As a result,the shape of the bottom field is more irregular,so this sorting method is not suitable for the division of the flat terrace of the slope farmland with a slope of 20-25.In the test area 2,the results of natural breaks and Equal Interval both correspond with leveling design regulation when the experimental subject is divided into 16portions.Obviously,the earthwork quantity caused by Natural Breaks is fewer,which is 12413.65m~3.In the case of 22 steps,the soil volume from Geographical Interval manipulation is minimum,compared with other methods,the specific number is 8830.60 m~3.And yet it has the highest elevation difference in neighboring terrace.Thirdly,we can presume the truth by comparing the maximum field difference,the average field difference,and the average field width.From the first test area,dividing the experimental subject from 17 to28 pieces of terraces,only do Equal Interval classification results accord with the construction regulation of horizontal terrace.Plus,the same sorting approach is still suitable in the second tentative extent,which meeting the construction regulation with fewer parcels of fields.It would efficiently broaden the field width to 5.69 meters when cutting into 15 sections,the mean adjacent field elevation difference is 2.70 meters.Ultimately,we can see Equal Interval classification is be appropriate for sorting sloping land in all conditions of our test.Moreover,it can maintain the balance of each height of terraces owing to the minus value of between the maximum and the average field elevation difference is the smallest.The value was confined within 0.22 meter in the first and 0.15 meter in the second experimental region.Therefore,this study confirmed the general applicability of Equal Interval sorting method for hilly lands division in the slope gradients between 20 to25.Finally,by observing factors fitting analysis results of soil volume,we can deduce that the mean field elevation difference is positively correlated with earthwork and their regression equations appearing as power function.The coefficient of determination is 0.99981 in the first and 0.99982 in the second test area.There is a positive correlation between the average field width and the earthwork.The results of first test region presents a linear relationship as the coefficient is 0.99983,although results for second experimental subject shows a power function with the determination coefficient of 0.99935.The number of earthwork is drastically interacted by the average field elevation difference and width.It demonstrates a certain linear relationship accompanying with the increase of the field width and the mean field elevation difference.A Principle Component Regression equation would reveal the trend of earthwork quantity caused by the average field elevation difference and average width in the first test region.While the tendency is quite varying in the second area,it is demonstrated by a Multiple Linear Regression equation.In this study,I have designed an experiment for leveling planning in sloping croplands where slope degrees converted from 20 to 25.It is verified that the high resolution digital elevation model,created by 1:2000 topographic map,could achieve the leveling goal for flat terraces division and calculating earthwork.The research could enhance the theory of land leveling in sloping arable land from the southwest China regions and provide an experience for flat terrace designing in conditional construction areas.Furthermore,given by the most optical sorting technique about terraces program,I have chosen the elevation difference,width and earthwork in fields from outcome of Equal Interval classification and build regression equations.It would apply an element for the cost control of land leveling in the hilly area.