Conducting a Comprehensive Physical Investigation on Uncontrolled Internal Soil Erosion Leading to Sinkholes in Anambra State, Nigeria

Abstract

Uncontrolled infiltration of water poses a significant environmental threat, capable of causing severe damage to structures and farmland if left unaddressed. In the context of Anambra state, Nigeria, uncontrolled infiltration has emerged as the primary cause of internal erosion, leading to the formation of numerous sinkholes scattered throughout the region. Consequently, this study aimed to analyse the physical dynamics of the soils surrounding these sinkholes within the state. The investigation was conducted across three distinct locations: Awka site 1 (6.2232°N and 7.0824°E), Awka site 2 (6.2220°N and 7.0819°E), and Agulu (6.3401°N and 7.1233°E). A total of 24 soil samples were collected and analysed, comprising of 15 samples from the immediate vicinity of the sinkholes and 9 samples obtained from areas located at least 2Km or more from the sinkholes. The parameters examined included pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Organic Carbon (OC), Organic Matter (OM), erodibility Factor (K), Moisture Content (MC), Bulk Density, Total Porosity and soil texture. The results revealed a range of pH values, with the piping zone exhibiting a pH of 5 and below, while the non-piping zone predominantly displayed a pH of 6 and above. This discrepancy indicates soil sodicity, suggesting potential challenges in terms of soil quality. Furthermore, the electrical conductivity values varied from 2.21 to 7.21 \(\mu\)S/cm, signifying differing levels of ion concentration within the examined areas. Additionally, the analyses indicated a substantial depletion of organic content, with the piping zone registering a meager organic content value of 2.43. Investigations of soil texture within the piping regions highlighted a notably low clay content, ranging from 2.5% to 6.7%. This finding suggested that significant drainage of the soil has potentially influenced the overall soil stability and the observations underscoring the presence of dispersive processes within the soil, further contribute to the prevailing conditions.