Soil assessment and mitigation of flash flood erosion using Ipomoe Carnea in Gombe town, Gombe state, Nigeria

Abstract

In many parts of the world floods occur more often and increase in size. In the tropics, it is partly or wholly caused by climatological factors, in-situ soil types (as soils with low infiltration rate are vulnerable to flooding); inadequate drainage network, topography and human factors. Gombe town is situated within an elevation of 628 m and 361 m above sea level (a.s.l). Topography is mainly mountainous, undulating and hilly with open plains and mean slope gradient of 5°, considered to be a high gradient for unprotected soils. This causes high surface runoff leading to excessive flooding and formation of gullies, cutting deep trenches that result in the destruction of residential houses and environmental disasters throughout Gombe town. The research work assessed gully erosion from high vulnerable sections in Gombe town affected by high fluvial floods. Field measurement was done using 50 m tape, GPS, satellite images and laboratory analysis. Laboratory analysis of soil particles sizes showed that mean particle sizes were 74.9 %, 14.1 % and 11.0 % for sand, silt and clay respectivly; the textural class for the entire study site was sandy clay. Porosity from the entire study area contains low volume of voids relative to the volume of solids. Bulk density was slightly high compared to the standards values. The soil chemical properties of the soil pH for the entire site mean (ESM) was 6.42. This indicates that the soils are slightly acidic which affect microbial activities on organic matter that enhance the binding of soils to resists erosivity of fluvial floods. People resorts to using vegetative cover of Ipomoe Carnea plant as mitigation measures to protect their vulnerable houses and farms from gully erosions because the stems interweaves and forms a thick cover that diffuses the high velocity water flow into laminar flow. The weaved stems traps, blocks and prevents the flood transported materials(soil, humus, gravels) in between the stems thereby prevents and slows soil erosion to the nearest minimum.