**3. Methodology**

#### **3.1 Field observations and basic data**

Sedimentological data is collected from 26 localities measuring 5–10 meter vertical sections mostly along the river and small tributaries in all the four areas. Once all outcrops were located, multiple measurements were collected including set-thickness, average grain sizes, and total thickness. Cross-bed sets thickness were measured in the z-plane with 30 cm scale and the minimum distance between measured vertical sections was roughly 0.50 km. The cross bedding sets in the study area are interpreted to be mostly dunes for the following reasons:

(1) cross bedding sets are truncated, (2) Paleocurrent directions were much less variable than one would expect in bars, (3) even if there are some bars within the data, they are usually made up of many layers of truncated dunes, and (4) all ripples observed on the outcrops were flowing in the same direction as the cross bedding sets rather than in a separate direction as see on a bar [12, 13].

#### *3.1.1 Cross-sets*

Cross-set heights were measured as these data can be used to reconstruct original bedform heights and formative flow depths. Trough- and planar cross bedding, which are genetically indicative of bed load transport, were present at nearly all studied field sites. They occurred predominantly in sand grade deposits, but omnipresent in pebble grade deposits of southern coalfields. To establish mean cross-set heights, the sampling strategy of [7] was followed.

#### *3.1.2 Grain size*

Grain sizes were measured at each outcrop. These measurements are taken using a standard 10 hand lens and a grain size card. Grains were identified in each set according to Udden-Wentword grain size scale. Grains within each set tended to be unimodal or at least largely represented by one size; this made finding the average size within cross bedding sets and was substituted for D50 which represents the median of the grain size distribution used in this study.

Sedimentological data so acquired from the Barakar exposures include grain size, cross bedding height, and bar-form height. These data were then used to determine multiple channel geometry, paleohydraulic parameters and paleo dynamics including: mean bed form height, channel depth and width, channel belt width, paleoslope, boundary shear stress, Darcy-Weisbach friction factor, paleoflow velocity, paleodrainage, and overall drainage area by the methods outlined below.
