利用高分立体影像构建东北黑土山地丘陵区切沟体积估算模型

分析侵蚀沟形态特征并构建体积估算模型,对大空间尺度探究切沟侵蚀具有重要意义。该研究选取位于东北黑土山地丘陵区穆棱市的典型样区,基于WorldView-2高分立体像对影像(0.5m分辨率),利用ENVI5.3提取同分辨率DEM,选择45条切沟,在ArcGIS10.3中提取并计算切沟顶宽(TW)、底宽(BW)、沟深(D)、断面面积(CSA)、沟长(L)、面积(A)及体积(V)等参数,分析形态特征及相互关系,构建切沟体积估算模型。结果表明:1)切沟TW、BW、D、CSA、L、A及V均值分别为5.63 m、2.82 m、1.05 m、4.94 m~2、81.90 m、470.54 m~2、428.53 m~3。断面BW/TW均值为0.48,切沟以V～U型为主。TW/D全部大于1,均值为5.95,表明沟道横向侵蚀较下切侵蚀速率更快;2)切沟体积与沟长(V-L)、面积(V-A)间均有极显著幂函数关系,相比V-L关系模型,V-A关系模型具有更小的平均相对误差和更大的纳什系数,可更准确有效预测切沟体积,建议将其作为东北山地丘陵区切沟体积估算模型;3)与黄土高原及干热河谷地区相比,东北黑土区切沟体积与面积幂函数关系的指数更小,而区内山地丘陵区较漫川漫岗区更大,反映出山地丘陵区更加强烈的切沟发育状况;切沟形态特征影响V-A模型构建的精度,建议将狭长度(L/TW)作为切沟分类指标构建切沟体估算模型。研究结果可为东北黑土山地丘陵区大空间尺度切沟侵蚀的定量模拟提供方法和依据。

Gully volume estimation model using high-resolution satellite imaging in mountainous and hilly regions with black soil of Northeast China

Severe gully erosion has posed a threat to food security in the black soil region of northeastern China, one of the largest grain-producing areas. Therefore, the prevention and control of gully erosion have become the top priority of soil and water conservation in recent years. Consequently, an estimation model of gully volume is a key step in modeling and mapping the gully erosion over a large scale, thereby to determining the erosive prone areas for better control of gully erosion. However, few researches were focused on modeling gully volume in this area. This study aims to explore the gully features, and then to build a gully volume model, finally assess the erosion parameters using the high-resolution remote sensing stereoscopic satellite imaging. The same high-resolution digital elevation model (DEM) was extracted from ENVI software using WorldView-2 stereoscopic satellite images (0.5 m resolution). ArcGIS 10.3 was selected to calculate gully morphological parameters of 45 gullies in a catchment located in the mountainous and hilly region of northeast China. The specific parameters included the top width (TW, m), bottom width (BW, m), depth (D, m), cross-sectional area (CSA, m2), gully length (L, m), gully area (A, m2), and the volume (V, m3). The results showed that the average values of TW, BW, D, CSA, L, A, and V were 5.63 m, 2.82 m, 1.05 m, 4.94 m2, 81.90 m, 470.54 m2, and 428.53 m3, respectively. The means of the width ratio between the gully top and bottom was 0.48, indicating that the cross-section of the gully was mainly in an intermediate shape (V~U shape). The mean of the ratio between gully top width and depth was 5.95, where all of gullies were greater than 1, indicating that the collapse of gully-wall was faster than that of deep-cutting in the study area. There was an extreme significance in the gully volume and the length (V-L) or area (V-A) of study areas. A very prominent relationship of power function was also found between the gully volume and length/area, and the determination coefficients (R2) of the volume estimation model were 0.57 and 0.90, respectively. Furthermore, the mean relative error and Nash coefficient further verified that the V-A model was more accurate and effective to predict the gully volume. The b value of power function was smaller in the black soil region of northeast China, compared with the Loess Plateau and the dry/hot valley regions, whereas, the b value was larger in the mountainous and hilly regions than in the rolling and hilly regions of Northeast China, indicating that the gully erosion was more serious in the mountainous and hilly region of Northeast China. The precision of the V-A model depended mainly on the gully features. Correspondingly, the ratio between gully length and top width can serve as an index of classification for better performance in modeling gully erosion. The finding can provide a scientific basis to assess the gully volume over a large scale in the mountainous and hilly regions of Northeast China.