Stream Order and Flow Pattern Assessment in Awka North and South LGAs of Anambra State of Nigeria using Shuttle Radar Topographic Mission (SRTM) and Satellite Imageries

Nnamnso Peter Udoudo, Ambrose Ndubuisi Ekebuike, Theresa Chioma Nwopi, Agulonu Angela Kosisochukwu


Abstract: - Streams are the channels through which water flow on the surface of the earth, from higher to lower elevations, or from the source, through intermediate to the trunk or destination. They are mostly natural (though there could be man-made) channels forming network of drainage systems on the surface of the earth. At the sources, water is seen oozing or zipping out from the soil or rocks, which gets larger with the channel length. The hierarchical position that a particular stream possesses in the stream connectivity or network within its basin is the order it is described to have. Thus, stream order is the hierarchical position a particular stream occupies in the stream network that it is found. Some source streams may be momentarily dry valleys or seasonal streams, containing water only during heavy rainy seasons. Others may have permanent water flow all year round. Awka North and South LGAs of Anambra state, the study area for this research has several of the “source or lower order” stream networks than the higher orders. Ignorance of the negative effects of building residential structure across the stream channels results in yearly floods, deep erosions, collapsing of buildings and loss of both lives and properties in the area. Little or no efforts has been made by the regulatory bodies and town planners to rescue this situation in the area. To assess the drainage network in the area and provide basic information of the stream orders to help in tackling all these environmental problems, this study aimed at providing environmental solution through acquisition, processing and interpretation of Shuttle Radar Topographic Mission (SRTM) and satellite imageries of the area using GIS technique. The objectives included acquisition of the required satellite imageries of the area, processing them to trace out the stream networks, assessing their flow directions and production of a stream ordering map of the area. Some recommendations made included the need for putting into consideration the flow channels before approval be given for siting of buildings and other structures in the area so as to avoid blockage of the stream channels and their corresponding consequences.

Keywords: Stream Ordering, Drainage Pattern, Stream Network, Satellite Imagery, SRTM.

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