MORPHO-HYDRAULIC CHARACTERISTICS AND SEDIMENT DYNAMICS OF TWO GRAVELLY STREAMS FLOWING OVER THE SIWALIK TERRAIN, CENTRAL NEPAL SUB-HIMALAYA

The Pantale Khola and the Thado Khola both are the fourth order streams originating from the Churia Hills and flowing on the gravelly terrain towards the north and ultimately mixing to the Rapati Nadi. The total area of the study area is 64 km2 . The fluvial condition of these streams originating from the Churia Hills along with their characteristics, sediment transport and sediment dynamics were studied. Geomorphic characterization of both the streams were accomplished using the help of topographic maps and satellite imageries. Five stream transects on each of the stream were surveyed for cross-sections and longitudinal profiles. Samples were collected from the thalweg of each transect for suspended sediment concentration and Wolman's pebble counting method was applied for establishing grain size distribution. The Rosgen classification of streams was applied to classify the stream reaches. Manning's roughness coefficient was calculated on the features as seen on the field and hence discharge was calculated. The streams have been classified as F4 type for the Pantale Khola and F4, F4b types for the Thado Khola. The bed load was calculated and hence total sediment load was also calculated. Both the streams show the eroding potential as found out from the stream power.