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Abstract

Agricultural irrigation and drainage canals in Taiwan are generally constructed using concrete. Concrete is used for the safety of conveyance efficiency. It also reduced loss and is structurally safe. The irrigation ditches and soil revetments in Taiwan fitted with a strong concrete lining. The smooth nonporous concrete surface makes the biology perch difficult and causes a monotonous flow. For these reason, an artificial materials-precast ecological concrete blocks (PECBs) was developed in this research. This was done in order to modify both the traditional concrete lining and the natural field materials in canal construction. Precast ecological concrete blocks (PECBs) were tested by hydraulic model experiments. These experiments used four kinds of height of projection under the condition of unaffecting conveyance efficiency. The experimental results show that the Manning roughness coefficients of PECBs, in a range of are greater than that of piling up cobblestone of concrete as side protection. The results also indicate that the Manning roughness coefficients are in inverse proportion to the discharges and in proportion to the bed slopes. The relationship between the roughness coefficient and surface roughness were estimated after regression analysis. The analysis of hydraulic characteristics and estimation of the Manning roughness coefficients, through this hydraulic modeling experimental study, can be used as a reference for the improvement in construction of irrigation and drainage canals.

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