Drainage basin morphometry and evaluating its role on flood-inducing capacity of tributary basins of Mayurakshi River, India

The Mayurakshi River Basin (MRB), one of the most flood-prone areas of India, registers flood almost every year. The present work intends to identify the relative capacity of the tributary basins of the Mayurakshi system (three sub-basins of Dwaraka, two of Kuye and eight of Mayurakshi) to induce flood in its lower stretch. Based on basic morphometric parameters (basin length, area, perimeter, relief, stream number, and length) computed from Survey of India topographical maps (1:50,000) and SRTM DEM (30 m) using ArcGIS 10.4 software, we have derived 15 morphometric indices (linear-2, areal-7 and relief-6). The principal component analysis (PCA) depicts that there are three clusters of indices on the varimaxrotated component plot with the centroid of the distribution in positive-positive (++) quadrant which signifies a peak flow. Besides, the bi-variate relations between basin lag time and different morphometric indices signal that all the variables except compactness coefficient, hypsometric integral, dissection index, and bifurcation ratio portray negative relations implying peak flow instead of sustained one. In this paper, we have developed a technique called the flood-inducing capacity index (FCI) to measure the contribution of a tributary river to its master based on the morphometric coefficient and basin area coefficient. The FCI depicts that sub-basin Mayurakshi-6 has topped the list with similar to 21% contribution to MRB flood while Mayurakshi-8 having less than 2% contribution lies at the bottom. Besides, Dwaraka-3,Dwaraka-1 and Mayurakshi-3 basins each having more than 8% contribution control flood in the lower stretch of the Mayurakshi system. A statistically significant positive correlation (R-2 = 0.75) between the maximum discharge measured for the nine sub-basins and the FCI and the area under curve (0.889) on ROC plot ground the validation of the proposed method.