PAPERS

Morphometric Analysis of Bhogdoi river basin using Geographical Information System
By – Jyotishmoi Phukan.

ABSTRACT
Geographical information system (GIS) has emerged as an efficient tool in delineation of drainage pattern and ground water potential and its planning. GIS and image processing techniques can be employed for the identification of morphological features and analyzing properties of basin. Basin morphometry is a means of numerically analyzing or mathematically quantifying different aspects of a drainage basin. In the present study, morphometric analysis of the Bhogdoi drainage basin has been carried using earth observation data and geographical information system (GIS) techniques. The morphometric parameters of basin can address linear, areal and relief aspects. The present study deals mainly with the geometry, more emphasis being placed on the evaluation of morphometric parameters such as stream order(Nu), stream length(Lu), bifurcation ratio(Rb), drainage density(Dd), stream frequency(Fs), texture ratio(T), elongation ratio(Re), circularity ratio(Rc) and form factor ratio(Rf), etc.. The Bhogdoi basin covers an area of 1006.76 sq.km. and is an 5th order drainage basin with mainly dendritic drainage pattern. Total number of streams is 846, in which 652 are first order, 155 are second order, 32 are third order, 5 are fourth order and 2 are fifth order streams. The length of stream segment is maximum for first order stream and decreases as the stream order increases. The drainage density(Dd) of the study area is 1.15 per km2. The study has strengthened in understanding the hydrological, geological and geomorphological characteristics of the Bhogdoi drainage basin.
Keywords: Morphometry, Bhogdoi river basin, earth observation data, geographical information system.

CONCLUSION AND FINDINGS
GIS and Remote Sensing techniques have proved to be accurate and efficient tool in drainage delineation and their updation. The morphometric analysis has been carried out through measurement of linear, areal and relief aspects of basins. It has been found that the study area is an 5th order drainage basin. Dendritic drainage pattern is seen in the hilly and plain parts of the drainage basin indicating the homogeneity in texture and lack of structural control. From the study it can be concluded that areas drained by drainage orders of 1st, 2nd, 3rd, 4th and 5th have bifurcation ratio between 2.5 to 6.4, indicating that these are not distorted by geological structures. The presence of the maximum number of the first order segments shows that the basin is subjected to erosion and also that some areas of the basin are characterized by variations in lithology and topography. The deviation of the mean stream length values from 0.98 to 6.53 clearly indicates the change in topographic elevation slope of the Bhogdoi Basin. The drainage density of study area is 1.15 km/km2 indicating moderate drainage densities. The moderate drainage density indicates the basin is highly permeable subsoil and vegetative cover. The Rf(form factor) value for study area is 0.07 indicating elongated basin with lower peak flows of longer duration than the average. The circularity ratio of the basin 0.24, indicating that the basin is elongated in shape having low discharge of runoff and high permeability of subsoil conditions. The length of overland flow(Lg values) of the study area is 0.43, indicating young topography. The slope of the basin range from a level slope in the plains(northern part) to a very steep slope in the southern part of the basin. Low relief to moderately relief is in the plains and high relative relief is in the hilly areas.

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