**4.3 Channel width (Wc)**

There are a number of empirical equations relating average bankfull channel depth to river channel width, many of which are thoroughly communicated and evaluated [13, 25]. However, the empirical equations used here are those they developed on river depth to channel width [1, 26] as

$$W\_{\mathfrak{c}} = \mathbf{8.88}^{\*} \; D\_{\mathfrak{c}}^{1.82} \tag{8}$$

$$\mathbf{W} \,\mathrm{c} = \mathbf{64.4}^\* D\_\mathrm{c}^{1.54} \tag{9}$$

Where, *W*<sup>c</sup> = width of channel, and *D*<sup>c</sup> = bankfull channel depth. Put down the value of channel depth in Eq. (8) we get the width of channel in between 408 m �817 m, and Eq. (9) indicate about 1380 m to 2956 m in the Rajmahal Barakar River.

#### **4.4 Sediment load parameter (F)**

So important is the type of sediment load in determining fluvial morphology that Schumm has proposed classifying alluvial river channels on the basis of the ratio of suspended load to bed-load and introduced the term bed-load, mixed load and suspended load channels ([27], p. 1579, **Table 1**). Although the ratio of suspended load to bed load is not determined directly but directly related to the percentage of silt and clay in the channel perimeter. And to calculate the percent silt-clay in the channel perimeter (M), following relationship is used:

$$\mathbf{M} = (\mathbf{S\_a}^\* \; ^\*\mathbf{W\_c}) + (\mathbf{S\_b}^\* \; ^\*D\_c) / \mathbf{W\_c} + D\_c \tag{10}$$

Where M = Sediment load parameter, *W*<sup>c</sup> = Bankfull channel width, *D*<sup>c</sup> = Bankfull channel depth, Sa = percent silt-clay in channel alluvium, and Sb = percent silt-clay in the bank alluvium. Detailed petrographic and geochemical studies in recent years have revealed that much of the clay size fraction of Barakar sandstones is authigenetic and secondly digenesis may completely alter the original silt-clay matrix may cause unknown error in estimation of M derived from Eq. (10), hence not used in present

*Analyzing Sedimentary Rocks to Evaluate Paleo Dimensions and Flow Dynamics of Permian… DOI: http://dx.doi.org/10.5772/intechopen.106994*

study. It is also possible to estimate M for the Barakar sandstone indirectly from Schumm's following equation:

$$\mathbf{F} = \mathbf{2} \mathbf{5} \mathbf{5} \,\mathrm{M}^{-1.08} \tag{11}$$

Where F (width/depth ratio) = *W* c/*D*c, and *W*<sup>c</sup> = bankfull channel width, *D*c = bankfull channel depth, and M = sediment load parameter. Substituting the estimated values of *W*c and *D*c, Eq. (11) indicates that Barakar River had a sediment load parameter of 3.07 and 3.52 for the Brahmini and Pachwara sub basin and between 5.41–6.92 in the northern sub basin of Chuperbhita and Hurra. Values from tables ([27], p. 1579, **Table 1**) indicate range in M, between 5 and 20 for mixed load rivers and less than 5 for bed load Rivers. Furthermore, the assessment of percentage of total load as bed load is estimated by using ref. [27] formula:

#### 55*=*M

where M denotes sediment load parameter.

By substituting values for M, the bed load comes out to be 17.74, 15.62, 10.14 and 7.94 respectively for Brahmini, Pachwara, Chuperbhita and Hurra sub basin respectively. Calculated values of M and percentage of total load as bed load in this study fall within the range of those established values for bed load rivers in the southern part (Brahmini and Pachwara sub basins) and mixed load rivers in northern part (Chuperbhita and Hurra sub basin).
