| The evolution of slope soil erosion is a complex dynamic process.Quantitative monitoring of the slope erosion process is of great practical significance for in-depth exploration of the erosion mechanism and construction of erosion models.However,the traditional contact erosion morphology monitoring method has shortcomings such as low efficiency and poor accuracy,which restrict the further development of slope erosion morphology research.In recent years,non-contact monitoring methods such as close-range photogrammetry technology and 3D laser scanning technology have gradually been widely used in soil erosion process monitoring and measurement due to their high efficiency and high precision.In view of the fact that the related application research of the above-mentioned technologies is not perfect,based on the indoor artificial rainfall simulation experiment,this paper uses close-range photogrammetry technology and 3D laser scanning technology to study the erosion evolution process of granite coarse red soil slope under long-term rainfall conditions.The various stages of slope erosion evolution and the characteristics of slope rill erosion were defined,and the measurement accuracy of the above two techniques was evaluated based on the actual measured soil erosion amount and rill morphology characteristics,which has promoted the digitalization and efficiency of slope erosion monitoring.The main research conclusions are as follows:（1）According to the different dominant erosion methods,the slope erosion process of granite coarse red soil slope can be divided into sheet erosion stage,rill development stage and rill maturity stage.In the sheet erosion stage（0 h-5 h）,the slope erosion develops slowly,and the slope erosion is dominated by sheet erosion.In the rill development stage（5 h-70 h）,the slope erosion developed actively,and the development of rill was affected by the combined action of headcut advance,bed incison and sidewall expansion.In the mature stage of the rill（70 h-100 h）,the slope erosion develops stably,and the rill erosion is dominated by the sidewall expansion.（2）The surface roughness of the slope surface increases continuously with the continuous rainfall.In the early stage of the test,the growth rate of slope surface roughness was slow,and it accelerated with the appearance and enhancement of the sidewall expansion.The coverage of coarse quartz grains on the slope surface has experienced a process of rising to dynamic equilibrium.Before the rainfall duration of25 h,the surface coarse-grain coverage showed an increasing trend with the rainfall duration;after 25 h,the surface coarse grain coverage showed a trend of erosion deposition dynamic balance with the duration of rainfall（between 47.68%-56.74%）.The coarse-grained quartz overburden on the soil surface is particularly significant in the area between rills and the upper part of the slope.（3）The rill length,width,depth and total surface area continued to increase as rainfall continued.The growth rate of rill length was the fastest in the early stage of rill development,and then gradually slowed down as the rainfall continued;rill width increased slowly in the early stage of rill development,and gradually accelerated with the continuous rainfall;The depth increases slowly in the early stage of rill development,the fastest in the middle stage of rill development,and gradually slows down in the mature stage of rill.The rill morphology at different slope positions showed different evolution characteristics.The width and depth of the rill at the upper slope increased most rapidly,followed by the middle and lower slopes.With the appearance and strengthening of the sidewall expansion,the growth rate of the total surface area of the rill is accelerating.（4）The soil erosion rate on the slope has experienced a process of increasing,decreasing and gradually stabilizing.In the sheet erosion stage,the soil erosion rate increased gradually with the rainfall,and the average soil erosion rate was 2.01×10-2kg/m2·min;In the stage of rill development and erosion,the soil erosion rate gradually decreased,and tended to be dynamic and stable,with an average soil erosion rate of1.32×10-2 kg/m2·min;in the mature stage of the rill,the soil erosion rate was relatively stable,and the average soil erosion rate was 1.24×10-2 kg/m2·min.（5）The two non-contact measurement methods have high accuracy in the measurement of soil erosion and rill morphology,and the measurement accuracy of soil erosion is 83.18%.In terms of soil erosion quality measurement,rill depth measurement and slope micro-topography reconstruction,close-range photogrammetry technology is superior to 3D laser scanning technology. |
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