Appraisal of design practices for river diversion structures

Master's Thesis from the year 2004 in the subject Geography / Earth Science - Geology, Mineralogy, Soil Science, Addis Ababa University, language: English, abstract: In this research work a case study of problems & comparative successes of 33 existing river diversion works in the Amhara region was assessed. It is tried to trace the causes of the major problems related to the design considerations and identify the knowledge gap between the current design practices and similar experiences in other countries. Besides, a GIS ArcView based database showing all features of the existing diversion structures is prepared for operational projects between the year 1971-2000. Among the many problems observed in the existing diversion structures problems of sedimentation at the headwork and main canal, downstream scouring, upstream flooding, damage on cut-off and apron, clogging of intake and scouring sluice outlets are found to be critical. The causes for these problems are attributed to the shortcomings in the hydraulic, hydrologic, and structural designs of diversion systems in addition to the improper operation and management of the schemes. These shortcomings in the design of the schemes are mainly problems in the delineation of backwater effect of the structure, the consideration for complete dissipation of energy of overflowing water, lack of knowledge for sediment consideration in fixing of sluice sizes & impact of sediment on the various components of the structure, the lack of consideration of the river morphology during the adoption of empirical formulae for design, etc. The major findings in the investigation and analysis of the observed problems revealed that the design of such systems is mostly adoptive, hardly standardised and do not consider local conditions. Different recommendations and alternative designs that are obtained from previous & recent research results are given regarding reducing the observed problems & improving the current design practice.