Abstract The effects of hydrology, soil structure, and geotechnics on soil loss and gully propagation on the Edda-Afikpo Mesas (southeastern Nigeria) were assessed by field studies, laboratory soil analyses, and GIS modeling.The study was carried out to attribute causality and recommend mitigation measures in the fast degrading settlement. Results of field studies indicate that two areas in the study region were of exceptionally negative pore pressure values (-654.03 kPa and -676.89 kPa, respectively) at ground surface level and significantly negative at 50 m below ground level (-163.53 kPa and -186.39 kPa, respectively); both areas aligned in the northeast-southwest direction. These two areas were further characterized by comparatively higher hydraulic heads (158 - 206 m), seasonal fluctuations of water level, and rapid drainage enhanced by springs flow. Developed models revealed that a slight water level increase in these areas, combined with high surface infiltration as a result of significant permeability values (ranged between 1.522×10-3 cm/s and 1.744×10-3 cm/s) would translate into positive pore pressure development and seepage flow due to hydraulic gradient towards the slope toes. Thus, the lower part of the slopes on the mesas experiences higher positive pore pressure build-up and particle uplift. This scenario most likely plays out seasonally and could be responsible for the toe failures that are predominant in the area. Results of laboratory analyses further revealed that the soils have geotechnical properties (significant natural moisture content, low to moderate plasticity, marginally low bulk density, and specific gravity and shear strength) that increased their soil loss and gully propagation potentials, exacerbated by hydrology, soil structure, and human factors. This study, therefore, advocates that the solution to erosion and gully menace in the area, and other places with similar geological, topographic, and climatic situations would require an integrated approach.

中文翻译：

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水文、土壤特性和岩土工程对下克罗斯河流域（尼日利亚东南部）埃达-阿菲克波台地沟壑传播的影响分析

摘要 通过实地研究、实验室土壤分析和 GIS 建模评估了水文、土​​壤结构和岩土工程对 Edda-Afikpo Mesas（尼日利亚东南部）土壤流失和沟壑传播的影响。建议在快速退化的定居点采取缓解措施。现场研究结果表明，研究区有两个区域地表层孔隙压力异常负值（分别为-654.03 kPa和-676.89 kPa），而在地平面以下50 m处显着负值（-163.53 kPa和-186.39 kPa，分别）；两个区域都在东北-西南方向对齐。这两个区域的进一步特点是相对较高的水头 (158 - 206 m)、水位的季节性波动、泉水流增强了快速排水。开发的模型显示，这些地区的水位略有增加，再加上由于显着的渗透率值（范围在 1.522×10-3 cm/s 和 1.744×10-3 cm/s 之间）导致的高地表渗透将转化为正由于朝向坡脚的水力梯度，孔隙压力发展和渗流。因此，台地斜坡的下部经历了更高的正孔隙压力积聚和颗粒抬升。这种情况很可能是季节性发生的，可能是该地区主要的脚趾故障的原因。实验室分析的结果进一步表明，土壤具有岩土特性（显着的天然水分含量、低至中等的可塑性、略低的容重、和比重和剪切强度）增加了它们的土壤流失和沟壑传播潜力，并因水文、土壤结构和人为因素而加剧。因此，本研究主张解决该地区以及其他具有类似地质、地形和气候情况的地方的侵蚀和沟壑威胁需要综合方法。