区域沟蚀野外调查方法--以东北地区为例

A field survey method for regional gully erosion:A case study in northeastern China

区域沟蚀调查结果是进行沟蚀治理的依据,但目前应用的遥感调查方法难以识别浅沟和规模较小的切沟。本研究在全国第1次水利普查土壤侵蚀抽样调查方法基础上,设计了基于调查单元的沟蚀调查方法,并在东北地区的辽宁省辽阳县和彰武县、黑龙江省嫩江县和内蒙古阿荣旗的112个野外调查单元进行了沟蚀调查。结果表明:辽阳、彰武、嫩江和阿荣旗4个县(旗)沟壑密度分别为1.70、0.61、1.51和5.04 km/km2,沟蚀强度分别为中度、轻度、中度和剧烈;4个县沟蚀条数分别为14.7、9.3、12.4和44.0条/km2,其中浅沟比例分别为46.9%、44.1%、71.0%和66.1%;以丘陵地形为主的辽阳县切沟比例高,以漫岗地形为主的嫩江县和阿荣旗浅沟比例高,以台地缓丘为主的彰武县沟蚀相对较弱,发生沟蚀时多以切沟为主;沟蚀主要发生在耕地,浅沟数量在旱地的比例高达88.8%~100%,切沟数量比例也达到40.1%~99.1%。本方法不仅能够客观、定量地反映区域沟蚀强度,而且能够通过在同一调查单元调查片蚀和沟蚀,实现片蚀和沟蚀强度评价和侵蚀贡献估算。

[Background] The management of ephemeral gully and gully erosion relies on their survey at regional scale. The remote sensing technique is the primary method for such survey currently,which,however,is hardly able to identify ephemeral gullies or gullies of small size. [Methods] This study provided a regional gully erosion survey scheme based on the stratified unequal probability areal sampling used in the First Water Resources Census（ 2010-2012） for interrill and rill erosion. The main steps of the method include making a survey maps and record forms of sampling units; field survey,such as photo shooting,record form filling,survey map drawing; determination and measurement of gully section;processing and calculation of survey data; and evaluation of gully erosion intensity. This newly developedmethod was later applied to four counties in Northeasern China,including Liaoyang county and Zhangwu county in Liaoning province,Nenjiang county in Heilongjiang province,and Arun Banner in InnerMonglia,covering 112 sampling units in total. The 4 counties belong to the mountain to the transition of the piedmont plain platform and hilly region. But Liaoyang is mainly in the typical hilly region,Zhangwu is mainly in the plateau to plain transition,which the platform characteristics are obvious,and Nenjiang and Arong Banner are mainly in the rolling hill region. [Results]The results showed that the densities of both ephemeral gully and gully were 1. 70, 0. 61, 1. 51 and 5. 04 km/km2 in the 4 counties,respectively,classified as the gully erosion grades of moderate,slight,moderate,and catastrophic. The numbers of both ephemeral gully and gully were 14. 7,9. 3,12. 4,and 44. 0 per square kilometer in the4 counties,in which the ephemeral gullies accounted for 46. 9%,44. 1%,71. 0%,and 66. 1%,respectively. The volume of gully erosion were 15 195. 8,11 489. 0,1 886. 5 and 14 060. 2 cubic meters per square kilometer respectively,which is mainly caused by gullies. It is clearly manifested that more gullies were developed in the hilly regions like Liaoyang and Zhangwu in Liaoning province,compared to the other type,while ephemeral gullies is dominant in the rolling hill regions,such as Nenjing in Heilongjiang province and Arun Banner in Inner Mongolia. These gullies mainly appear in the cultivated lands. The proportions of the farmand varied between 23. 3% and 55. 5% for the 4 counties,while the numeral percentage in farmland were between 88. 8% and 100% for ephemeral gullies,and between40. 1% and 99. 1% for gullies. Without appropriate conservation practices, ephemeral gullies can develop into gullies in a short term. [Conclusions]It is critical to take effective actions on the gullies as well as the ephemeral gullies,especially on the cultivated areas. The method provided in this study could assess both ephemeral gully and gully erosion quantitatively and objectively for regional scale,and evaluate contributions of sheet erosion and gully erosion respectively by combining the interrill and rill survey in the same sampling unit.