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E-International Scientific Research Journal ISSN: 2094-1749 Volume: 3 Issue: 2, 2011 Circularity ratio (R e ): It is the ratio of area of river basin to the area of circle having the same perimeter as the basin (Miller, 1935). Like form factor, it is also a dimensionless ratio to express outline of drainage basin (Strahler, 1964) and R e is uniform between 0.6 and 0.7 for homogenous rock types and 0.40 and 0.5 for quartzitic terrain and is influenced by length and Df of streams, geological structures, vegetation, climate, relief and slope of the basin. Sinuosity index (S): It is the ratio of channel length and river valley length (Muller, 1968). Sinuosity index reveals the topographic and hydraulic conditions of streamlines and it varies from 1.1 to 4.0 or more and those having S less than 1.5 called sinuous and with 1.5 or more than 1.5 are called meandering. Stream channels usually originate in sinuous form, which depends on underlying rock structure, climate, vegetation and time. The average Sinuosity index of DRB is 1.11. Data Integration and Natural Hazard Vulnerability Assessment The morphometric results have been integrated and superimposed with other GIS base maps to natural hazard vulnerability assessment. Mainly three types of natural hazard identified within the third order sub basins i.e. erosion, landslide and flash flood hazard. A brief description on each type of hazard vulnerability within all the twenty three third order sub-basins given as below: Erosion Hazard Vulnerability: Increasing first order streams, increasing drainage density and frequency are the main morphometric parameter for erosion hazard vulnerability but the frizzled geo-ecological parameters (i.e. stressed and crushed geology, active faults and thrust, degraded land use pattern and lineaments etc.) are accelerating factor for the hazard vulnerability. Therefore out of total 23 sub basins 15 sub basins have high erosion vulnerability whereas 4 sub basins found for moderate and 4 sub basins found for low erosion hazard vulnerability (Fig. 5 and Table 6). Landslide Hazard Vulnerability: Although the study area is highly vulnerable for seismic landslide activity due to active lineaments such as thrusts (MBT) and number of faults but it experienced that the area is equally vulnerable for non-seismic landslide during rainy season because of degraded land use pattern whereas the morphometric factors for landslide vulnerability are same as for erosion hazard vulnerability. Fig. 5 and Table 6 depicting the spatial distribution of the landslide vulnerability within the third order sub basins. Out of total 23 sub basins maximum 19 sub basins have high landslide vulnerability whereas only 2 sub basins found for moderate and 2 sub basins found for low landslide hazard vulnerability (Fig. 5 and Table 6). 83
E-International Scientific Research Journal ISSN: 2094-1749 Volume: 3 Issue: 2, 2011 22 4 1 Dabka Watershed Erosion Hazard Vulnerability 2 3 23 13 14 16 15 0 0.5 1 2 Km 1:25000 22 4 1 Dabka Watershed Landslide Hazard Vulnerability 2 3 23 13 14 16 15 7 5 6 9 10 11 12 21 17 Index High 19 18 20 7 5 6 9 10 11 12 21 17 Index High 19 18 20 8 Moderate Low 8 Moderate Low 22 4 5 6 7 1 Dabka Watershed Multiple Hazard Vulnerability 8 2 3 23 9 13 10 11 14 12 16 21 15 17 Index High 19 Moderate Low 18 20 22 4 5 6 7 1 Dabka Watershed FloodHazard Vulnerability 8 2 3 23 9 13 10 11 14 12 16 21 15 17 Index High 19 Moderate Low 18 20 Figure 8: Natural Hazards Vulnerability (Flood, Erosion, and Landslide=Multiple: Clockwise from Upper Left to Lowe Left) Flood Hazard Vulnerability: Mainly two types of floods are common throughout the Himalaya i.e. flash flood and river-line flood which are among the more devastating types of hazard as they occur rapidly with little lead time for warning, and transport tremendous amounts of water and debris at high velocity. Intense rainfall (IRF) is very frequent cause for flash flood and river-line flood in the study area which play a key role for flash flood and river-line flood. The main meteorological phenomenon causing intense rainfalls in the region are cloudbursts, stationarity of monsoon trough and monsoon depressions. Flash flood in the region cause great loss to life and property and poses serious threat to the process of development with have far-reaching economic and social consequences. In order to that it is quit important to assess the flood hazard vulnerability due to morphometric parameters and geo-environmental factors. The major morphometric parameter of flood high hazard vulnerability is decreasing Elongation ratio (R e ). The spatial distribution of flood hazard vulnerability with in the third order sub basins suggesting that out of total 23 sub basins 6 sub basins have high flood vulnerability whereas only 5 sub basins found for moderate and 12 sub basins found for low flood hazard vulnerability (Fig. 5 and Table 6). 84
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