Permeability Characteristics of Lower Niger Floodplain Sediments and their Implications for Drainage and Flood Mitigation

Rising flood-related damage to infrastructure across the Lower Niger floodplains has increased the need to understand the permeability of floodplain sediments, both to explain the persistence of flooding and to assess the feasibility of dewatering these areas. These floodplains occupy about 7% of the Niger Delta and are under growing pressure from intensive development. Reliable permeability estimates are essential for flood control, groundwater flow assessment, and contaminant transport analysis, all of which are critical to sustainable land and water management in the region. This study evaluated the permeability of stratified floodplain soils using field pump tests and laboratory constant-head tests, alongside particle size distribution analysis on randomly selected samples from eight boreholes. The particle size data were also used to estimate permeability through an established empirical equation. Permeability values obtained from the field pump test ranged from 1.52 × 10⠻³ to 1.67 × 10⠻³ m/s, while constant-head test values ranged from 4.0 × 10⠻⠴ to 7.1 × 10⠻³ m/s. Empirically derived permeability values averaged 4.7 × 10⠻³ m/s. Comparison of the three methods showed strong agreement, which is attributed to the high grain uniformity of the sediments. The findings indicate that, in uniform granular floodplain soils, field, laboratory, and empirical approaches can produce comparable and acceptable permeability estimates. The measured permeability values further suggest favourable drainage conditions; where hydraulic connection exists between the surface and underlying sandy layers, natural drainage and dewatering could help reduce prolonged flooding in the Lower Niger floodplains.