Stream ordering is the first and the basic step in morphometric analysis. Different classifications of stream ordering have been suggested by [32] [33] [34] [35] [36]. But for the sake of simplicity, Strahler classification for stream ordering has been adopted. According to the Strahler ordering system the smallest unbranched stream segment is designated as first order, where two first order segments meet it forms second order, where two second order segments meet it constitutes a third order and so on [15]. The highest order stream is the trunk stream where all the water and sediment discharge of catchment accumulates and passes through it. Sixth order is the highest order stream encountered in the Shahzad watershed.

The total number of stream segment present in each order is termed as stream number and the value of stream number decreases with increasing stream order. According to Horton (1945) “law of stream number”, the logarithms of the stream number plotted against the stream order follows the inverse geometric sequence and the points lie on the straight line although some of the points may show little deviation from the linear path. In Shahzad watershed, there are 1500 first order streams, 349 are of second order, 82 are of third order, 18 of fourth order, 3 of fifth order and one (main Shahzad stream) is of sixth order. Figure 8 shows the negative correlation when stream order is plotted against the stream number.

Cumulative length of all stream segments of a particular order is the stream length of that order. Stream length is generally higher in lower orders, as stream number increases the length of the stream decreases and vice-versa. Large number of stream with shorter length develops on the bed rock of less permeable formations as compared to the well-drained watershed where small number of relatively longer streams are developed [37]. According to the Horton’s (1945), “law of stream length”, the length of streams of each order in a drainage basin tends closely to approximate a direct geometric ratio. Plotting of stream order against stream length follows the linear pattern which indicates the homogeneous rock material exposed to weathering and erosion. The deviation from the general pattern is an indication, that the terrain is characterized by the variation in lithology and topography. Longer length of the streams is indicative of flatter gradient [38]. The stream length of all orders are individually measured in Arc GIS 10, the stream length value of first, second, third, fourth, fifth and sixth orders are 943.20 km, 366.36 km, 199.64 km, 124.33 km, 28.77 km and 61.8 km respectively. The regression plot of stream order against stream length (Figure 9) shows the deviation in stream length at sixth order (which should be smaller than fifth order stream length in case of general pattern) may be due to the uniform lithology, gentle slope and low gradient in the topography.

Mean stream length is the dimensional property which reveals the characteristics of drainage network and its contributing basin surface [15]. It is the ratio of total stream length of a particular order to the number of streams of that order. With the increase in stream order the value of mean stream length increases, the two show positive correlation (Figure 10).

Stream length ratio is calcutated by the ratio of mean length of streams of a given order to that of the next lower order [32]. The value of stream length ratio ranges from 0.231 (for V/IV) to 2.148 (for VI/V). The decimal value of stream length ratio indicates that mean length of the streams of higher order is less than the stream length of next lower order. The variation in the stream length ratio

may be due to change in topography and slope, indicating the late youth stage of geomorphic development in the streams of the concernt area [19] [39] [40].

Bifurcation ratio is defined as ratio of number of stream segments in a given order to that of the number of stream segments of next higher order [41]. The bifurcation ratio is regarded as the sign of relief and dissection [32]. The watershed where geometric structures do not distort the drainage pattern, their value of bifurcation ratio ranges between 3 to 5 [42]. The lower value of Rb indicates that the watershed is structually less dominated without distortion in the drainage pattern [43]. According to Strahler (1957) the value of Rb shows small variation in different regions or different environment except where powerful geological structures dominate.

In Shahzad watershed the value of bifurcation ratio ranges from 3 to 6 (Table 2), higher values indicate that the drainage is structurally controlled in some part of the watershed while the lower values show small variation among them and indicate less structural disturbances. Mean Rb of the watershed is 4.422.

The concept of drainage density was proposed by Horton [45] as the closeness of spacing between the stream segments. Drainage density is the measurement of

total stream length of all order in the given basin to the per unit area. Drainage density is indicative of landscape dissection, runoff potential, vegitation cover, climatic condition, runoff potential, infilteration capacity of land, rock and soil property of the basin [46] - [51]. Low drainage density is produced in the areas of highly resistant or permeable sub surface material, dense vegetation and low relief. The high drainage density generally occurs in areas of impermeable and weak sub surface material, high relief and sparse vegetation [43]. Langbein [52] recognized the importance of drainage density as a factor of determining the time of travel by water in a given basin. Low drainage density leads to coarse drainage texture, whereas high drainage density results in fine drainage texture.

The overall drainage density of the Shahzad watershed is 1.567 (low) however the higher drainage density is observed in the areas where impervious granite and gnisses are exposed (Figure 11). Low drainage density is found in the southern periphery where resistant and permeable rocks are present. The third zone is characterized by the wide stretch of alluvium, where in general the drainage density is very low except in areas where stream segments of all orders reach to principal stream, thereby increasing the drainage density in a particular area. The drainage density in the alluvial part of the watershed is low due to high permeability and infiltration.

Stream frequency is the total number of streams of all orders per unit area (Horton, 1932). Like drainage density, stream frequency is also a similar parameter to measure the drainage network of the basin. High stream frequency is generally related to impermiable sub surface material, low infilteration capacity, sparse vegitation and high relief [50] [51] [53]. In Shahzad watershed, stream frequency is 1.77 (low) which suggests that large part of the watershed is covered with permeable lithology i.e alluvium. However stream frequency is locally high, especially in those parts of the basin where granite and gnisses are exposed.

Drainage texture depends upon climate, rainfall intensity, infiltertion, soil type, vegetation and climate [54]. In the initial stage of erosion cycle the drainage texture is found to be coarse in nature. Smith (1950) classified drainage texture into three categories, i.e. below 4 is course texture, from 4 to 10 is medium texured and above 10 is fine textured. The value of drainage texture in Shahzad watershed is 7.698 which falls in the medium textured category (Table 3).

Form factor is defined as the ratio of area of the basin to the square of its basin length [45]. The value of form factor will always be greater than 0.7854 for a perfectly circular basin, whereas samller value is indicative of more elongated basin. The circular basin will have high peak flow for the shotter duration, whereas an elongated basin with small form actor, has low peak flow for longer duration. The value of form factor in the Shahzad watershed is low (0.224) indicating the elongated shape of the basin, further it also suggests that the area has low peak flow value for longer duration which can be easily managed as compared to a circular basin.

Circulatory ratio as the ratio of the river basin area to the area of a circle has the same perimeter [55]. It is a dimensionless ratio to express the boundary of the basin; its value varies from 0 to 1 in line and circle respectively [15]. The variation is influenced by the frequency and length of stream, geological structures, climate, vegitation, slope and relief of the basin. In the present case the circulatory ratio of Shahzad watershed is 0.215 which is indicative of low relief and less structurally controlled drainage network.

Elongation ratio is a ratio between the diameter of the circle of same area as that of drainage basin and the maximum length of the basin. The value of elongation ratio defines the shape of the basin and depends on the climate and topography of the basin [15]. The value generally varies from 0.6 to 1, where 0.9 - 1.0 is circular, 0.8 - 0.9 (oval), 0.7 - 0.8 (less elongated), 0.5 - 0.7 (elongated) and <0.5 (more elongated). The elongated basin is less efficient in run-off discharge than a circular basin (Singh and Singh, 1997). In Shahzad watershed the value of elongation ratio is 0.533, which indicates that the watershed is elongated.

The infilteration number is the product of drainage density and stream frequency. It is observed that higher values of infilteration number indicate low infilteration and high runoff [56]. The low infilteration capacity results in high drainage density which indicates the impervious sub surface material and vice versa. The value of infilertation number in the study area is low (2.783), which indicates high infilteration capacity and less drainage density. The alluvial region has high infilteration capacity, thus the drainage density in this region of Shahzad watershed is low, and hence it suggests low surface runoff.

The basin shape is the ratio of square of the basin length to its area and mainly governs the rate at which water is supplied to its principal channel. The value of basin shape of the study area is 4.45 (Table 3).

Horton (1945) describes the length of overland flow, as the length of the water flow path over the ground before it confluences to the adjecent stream channel. The length of overland flow is nearly half of the reciprocal of drainage density. Lg is inversally proportional to the average slope of the channel and is synonymous with the length of sheet flow to a large degree. Rainfall intensity, infiltration rate, soil, landuse/cover, slope etc are the factors that affect the value of Lg. Maximum length of overland flow marks the youthful stage whereas lower value of Lg at the old stages [27]. The length of overland flow in the watershed is 0.319, indicating low drainage density and high infiltration, thereby suggesting into less surface runoff.

Drainage intensity is defined as the ratio of stream frequency to the drainage density [57]. Low values of drainage intensity indicate little effect of drainage density and steam frequency on the extent to which the surface has been lowered by the agent of denudation. The value of drainage intensity in Shahzad watershed is 1.132. The low value of drainage density, stream frequency and drainage intensity suggest that the surface runoff is slowly removed from the basin.

The term constant of channel maintenance (C) is defined as the inverse of drainage density [41]. The drainage basin with a higher value of C will have low value of drainage density and vice-versa. The low value of drainage density results into higher value of C reveals the control of lithology with surface of high permeability. In Shahzad watershed the overall value of C is 0.638, indicaes low value

of drainage density as larger part of the basin is dominated by alluvium which possess higher permeability hence, resulting into higher value of C.

Basin relief is calculated by taking the difference between the elevation of the highest and the lowest points within the watershed. Basin relief is an imporant parameter to understand the morphology of drainage development, surface and sub-surface water flow direction, erossional character like volume of sediments transported and landform development in a basin [58] [18]. The basin relief of the Shahzad watershed is 215 m which suggest less difference in elevation.

Relief ratio is a dimensionless parameter and defined as the ratio between the basin relief and longest dimension of the basin parallel to principal stream [41]. Relief governs the conversion of potential energy to kinetic energy of water that flows through the basin [59]. It is a measure of gradient aspect of the watershed, indicating the intensity of erosion processess operated on the slope of the basin. The high value of relief ratio indicates steep slope and high relief and vice-versa. The value of relief ratio in the watershed is low (0.003) indicating the gentle slope and low relief resulting into low peak basin discharge and less erosion.

Strahler (1964) defined the ruggedness number, as the product of the basin relief and drainage density. The high value of ruggedness number not only indicates steeper slope but longer length as well. Rn in the Shahzad watershed is 0.336 showing low value with gentle sloping area and low stream frequency. Since the ruggedness number in the basin is low thus the erossion and the dissection in the Shahzad basin is also low.

The asymmetry factor is calculated to establish the relation between the lateral shifting in a basin with reference to main water course. It is used to evaluate the tectonic tilting of the basin along with the direction of tilt [63] - [69]. This index includes the direction of differential tectonic activity and is also sensitive to uplift and subsidence of discrete blocks versus broad tilting [70]. The Af-index is calculated by the following formula

Af = (Ar/At) 100

where Ar is the area of right side of the basin along the trunk stream (facing downstream) and At is the total area of the basin. If Af > 50, it suggests that river has shifted towards the left side of the downstream and the basin has uplifted from the right side. When Af value is <50, it indicates that the river has shifted towards the downstream right side and has uplifted from the left in the drainage basin, whereas Af value equals to 50 shows perfect symmetry with no tilting. Variation in Af value lesser or greater than 50 indicates tilting either due to active tectonic or lithological control [64]. The main Shahzad River was considered to calculate the Af index of the watershed, further the basin was divided into northern and southern halves to calculate the amount and direction of tilting at local level. The Af factor of Shahzad watershed is 50.69 indicating that the river has shifted towards the left, and the basin is slightly uplifted from the right (Figure 12), which confirm to the findings by Prakash et al. (2016). Further, when the basin is divided into northern and southern zone, it has been observed that the Af-index is 60.15 in the southern zone indicating the uplifting at the right side where as in the northern zone Af-index is 35.85 indicating the subsidence at right side.

The sinuosity of a river is defined as the curvilinear distance to the linear distance between the ends of the curve or the degree to which the river has departed from the straight line. The river with the sinuosity index greater than 1.5 is referred as meandering river, whereas <1.5 is considered as sinuous river [71]. The channel index calculated in this investigation is the length of a reach as measured along the channel divided by the airline distance between the two end points of the reach [72] [73].

In the study area, the main river channel is divided into three segments viz.,

First segment (head to pre Govindsagar reservoir), Second segment (Govindsagar to pre Shahzad reservoir) and the third segment (post Shahzad reservoir to the mouth). The values of channel index for first, second and third segments are 1.83, 1.16 and 1.15 respectively (Figure 13). The river at the first segment is highly meandering in its pattern, as it flows between the dissected plateau where the surface runoff is higher resulting in erosion of alluvium over, whereas in the second segment it continues to flow on alluvium but the volume and velocity of water is restricted by the Govindsagar dam, hence resulting into low sinuosity value. The third segment has the lowest value of channel index, probably due to short distance and the resistant bed rock on which the river flows. Figure 14 shows the sinuosity status at different reaches of the Shahzad River.