KINEMATIC ANALYSIS OF FLOOD RUNOFF FOR A SMALL-SCALE UPLAND FIELD

In Japan, many sloping fields are being reclaimed by the Ministry of Agriculture, Forestry and Fisheries to increase the upland field areas. To predict the flood discharge from these fields, a study was undertaken from one reclaimed sloping field, in the Hiroshima prefecture, with an area of 4.55 ha. For modelling purposes, the widely used kinematic wave equations and method of characteristics were used. Rainfall and runoff data were collected for a period of 6 years (1984-1989) from the field, for both furrow and non-furrow conditions and were used in these analyses. Manning, Darcy and laminar resistance equations were used and Manning's equation was found to be the best of the three. Manning's roughness coefficient (n) for furrow flow and equivalent roughness (N) for non-furrow flow conditions were determined and are presented in tabular form. Application of the non-furrow flow equation to the furrow flow condition required selecting an adequate equivalent roughness. Finally, verification of time of concentration, velocity of sheet or furrow flow and runoff coefficient were made both for furrow and non-furrow conditions, and these are graphically presented.