Assessment of Morphological Aspects of Kushiyara-Monu River System

Abstract

As time changes, hydro-morphological features of Barak River started changing since 1960’s and hereafter major flow of the Barak River being mostly discharged by the Kushiyara river. Monu River is an important tributary of Kushiyara River. Realizing the importance of the changed hydro-morphological characteristics of the hilly river Kushiyara and Monu, this study has been conducted to investigate the morphological characteristics and sediment transport phenomena of these two rivers, to determine the relationship between discharge parameter and width-depth ratio and other geometrical properties. Sediment load were calculated and were compared with the observed sediment data for selected years. Study of bankline shifting was carried out using satellite images for the year 1997 and 2006. From the graphical and quantitative analysis of cross sectional area of Kushiyara River it is observed that sedimentation is portrayed in the period of 1972 to 1992 whereas erosion can be illustrated in the period from 1992 to 2004. Again during 1992 to 2004, area was increased due to erosive characteristics of the River. Area-Elevation analysis, mean bed level analysis, thalweg analysis, analysis of section factor of the river also agrees with this observation. The available cross-section data of Monu River cover a very short duration (2002 and 2005). So it was not possible to observe any significant morphological change during the study period, except little reduction of cross-sectional area at section No. 4 and 5. Calculated sediment load by using Ackers and White formula has shown better agreement with the observed sediment load than that using Engelund-Hansen equation for Kushiyara River. On the other hand, for Monu River Engelund-Hansen equation gives better result than the Ackers and White equation. From the superimposed images of Kushiyara and Monu River for the year 1997 and 2006, it was found that significant change occurred in the meandering lower stretch of Kushiyara River and almost entire reach of Monu River. Around 3.53 km2 area were eroded and 5.43 km2 area were deposited along the bank line of Kushiyara River whereas, 2.4 km2 area were eroded and 3.22 km2 area were deposited along the bank line of Monu River.