Topographic constraints to urban land uses in Enugu, Nigeria

Empirical investigations show that Enugu is constrained in urban land use by the ruggedness of its topography, the peculiarities of its relief, and its lithological and drainage characteristics. A granulometric analysis of soil samples collected at random from open spaces (non-concrete areas within the built-up environment) revealed a sequence of over 50% clayey material at a depth of 1.2 m below the ground surface. With an annual rainfall of over 1500 mm, such a significantly clayey lithology sets the stage for violent operations of catenary processes by extensive overland flow. The dissection of the topography by a maze of rivers over such a vulnerable lithological setting has wide implications for fluvial activities. An average drainage density of 1.4 km km ^-2 and a ruggedness number averaging 481.85 indicate severe topographic constraints to urban land uses in general and to accessibility and transport development in particular. Hypsometric analyses effectively highlighted the importance of relief as a constraining factor to urban land uses in Enugu. The study revealed that any attempt to enhance accessibility in order to achieve a full spatial integration of the area would imply the construction of numerous costly bridges and fly-overs. Relying mainly on the technique of morphometry, various topographic details were utilized to synthesize a morphoconservation map and land-capability map. As invaluable instruments for proper urban land evaluation, these highly specialized maps are proposed as good bases for urban land use planning, allocation and management.