Delineation of Topography with respect to Mean Sea Level using the Geoid Method for B-Dere and Ejama-Ebubu in Rivers State, Nigeria

Abstract

Accurate leveling is critical to every hydrogeological investigation. Areas of study in need of data point leveling include flooding, design of drainage infrastructure, mapping of drainage basins, solute/contaminant transport, groundwater recharge and discharge zones. The objective of this paper is therefore to employ the use of geoid method in the correction of Global Positioning System (GPS) derived elevation values to delineate the natural topography vis-à-vis the mean sea level at B-dere and Ejama-Ebubu in Rivers State Nigeria. The data revealed that B-dere study site located  about 19 km southeast of Ejama-Ebubu was found to be below sea level as all five sampling points returned elevation values varying between -6.4 m-msl and -3.5 m-msl. Four sampling points located northwest of Ejama-Ebubu study site out of the thirteen positions occupied also yielded elevation values differing between -4.2 m-msl and -1.1 m-msl. These areas are topographic troughs and subject to flooding - a realization impossible to reach using the GPS elevation reading directly since results are always positive.