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In most studies on flood risk in Nigeria, priority is given to urban flood risk than rural flood risk. Smallholder farmers who mostly inhabit rural areas and flood plains are known to be at great risk of flooding, but to date, there have been no studies on the impacts they experience and how they cope with these impacts.
To establish the existence of significant change in precipitation in the study area, statistical analysis of precipitation data was conducted using linear regression and non-parametric Mann Kendall test. Landsat satellite images for 1986, 2003 and 2016 were obtained from the United States Geological Survey’s (USGS) website and used to collect and analyze data related to land use.
To determine flood risk in the context of land use change, the HEC-HMS model version 3.5 was used. Land use maps corresponding to 1986, 2003, and 2016 LULC conditions were analysed and prepared for the calculation of CN values using Soil Conservation Service (SCS-CN) method. CN map was prepared by integrating the maps of hydrologic soil groups and land use in ArcGIS software.
Based on selected morphological parameters, a flood risk map was developed for the study area. The morphologic flood risk showed that most parts of the basin face moderate flood risk. Higher runoff values were observed under 2016 LULC conditions mainly due to intense deforestation relative to those of 1986 and 2003. The results indicated that runoff and peak discharge are significantly affected by deforestation instead of changes in the rainfall pattern. Flood inundation maps of the study area were prepared for the flood events of 2012 and 2015. Maximum depth for the 2012 and 2015 flood events was calculated as 10.58m and 7.39m, respectively.
The socioeconomic aspects of the research were conducted using household survey method. Using snowball sampling techniques, 400 flood-affected households were selected. The results show that the adaptive capacity of smallholder farmers in the study area remains very low and hampered by several factors such as poverty and weakened social networks. The synopsis of the examined variables leads to the following conclusion: Instead of climatic factors – as one indicator of vulnerability – it is social inequality and poverty in the region as well as the structural economic differences between various groups that mainly drives vulnerability in the study area.
Groundwater is an important resource in Sub-Saharan Africa to supply water for domestic, industrial, mining and irrigation for agricultural purposes. In Ghana, groundwater supply program is mostly pragmatic to give people drinking water, however to ensure sustainability a long term groundwater management system is essential. One such approach is the use source protection (well protection) with the declaration and installation of protection zones. To achieve the goal of this research three hypothetical questions were asked which relates to the Availability and Vulnerability of groundwater, and the use of an analytical model to estimate source protection zones (SPZ). The regions of Adansi, Lawra, Sunyani and Sekyere West were chosen as study areas to test the hypothesis of this research with detailed investigation concentrating on Adansi area. The overall aim from the study areas was to estimate SPZ for Granite, Phyllite, Schist, Sandstone and weathered materials and give recommendations as to which activity should be permitted or otherwise within each of these zones. The available groundwater for a particular well or location was determined based on its hydraulic conductivity and specific capacity of a well. Regionalization of the available groundwater was achieved by comparing the results of the hydraulic conductivity and specific capacity with the regional structural map. To determine the vulnerability of the available groundwater, the radius of influence (ROI) for the different boreholes was determined using Sichard and Dupuits formula whilst for Source protection zones, Darcy and the volumetric equation was used. Results of hydraulic conductivity estimated from pumping test data for the five major rock types showed a trimodal distribution (E-5, E-6 and E-7 m/s). There was a general trend of decreasing hydraulic conductivity to decreasing transmissivity. Results of plots of specific capacity verses hydraulic conductivity shows that only rock types with hydraulic conductivity greater than E-5 m/s yields sustainable groundwater supply. Three aquifer types were encountered in the study areas which were pore aquifers in shallow or alluvial, regolith and fracture aquifers in bedrocks. High hydraulic conductivity from the different rock types corresponds to higher ROI. The results of hydraulic conductivity, specific capacity, ROI and SPZ are used as input parameters for the estimation of the suitability of a groundwater source. A ranking matrix was developed for easy interpretation of hydrogeological data by combining the results of the input parameters into a single score. Results from the ranking matrix were used to determine specific regulations for the various aquifers in the study areas. Within the fractured crystalline rocks with k ≥E-5m/s siting of wells should target fracture zones whilst pumping during abstraction phase can exceed 15m3/s/m. The intermediate source protection zone should be at least 150m. Conclusions from the study could be applied in other areas of Ghana and be implemented during the initial development, abstraction and groundwater policy phases of other groundwater projects.