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  • Author: Balai Chandra Das x
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Abstract

The largest grinding stone episodically stored in pothole is not only responsible for growth of pothole size but also determines its shape. This paper examines the largest grinding stone found in cylindrical potholes and their role in pothole growth using empirical analysis. The largest grinding stone from 34 randomly selected potholes, developed on the riverbed of Subarnarekha River at Ghatshila, Jharkhand, India, were analyzed to have an insight into 1) their sizes and shapes; 2) controls on grinding stone shape; and 3) roles of largest grinding stone on streambed pothole growth. Strong correlation coefficient between the size and weight of grinding stones reveals their similar specific gravity. The pothole depth was proportional to the diameter of the largest grinding stone in it. Concave pothole-floors developed because of abrasion by grinding stones atop floor. A force applied on largest grinding stone depends upon not only eddy velocity within pothole but also on shape of the stone.

Abstract

Present study is on the interdependent nature of hydraulic parameters and morphometric variables of a bedrock river. In this study, using dumpy level, GPS, satellite images and some mathematical equations a data set on hydraulics and morphometric variables of a bedrock channel, named Bhatajhor, of eastern India was generated. That data set was used to (1) find out impulse-response relations between hydraulic variables (2) find out relations between morphometric variables and (3) find out relations between hydraulic and morphometric variables. Seven equations (5–11) were formulated based on this empirical study to the end. The seven empirical relations, most of which include only two variables, involve channel cross-section dimensions (area, width, mean depth, maximum depth, width/depth ratio, hydraulic radius), slope and hydraulic variables (velocity, kinetic energy, stream power, Manning’s n factor, Chezy’s C factor and shear stress). Observation shows relatively higher coefficient of determination (R2) between variables like velocity and Manning’s n factor (0.67), velocity and Chezy’s C factor (0.67), slope and τ (0.89), w/d ratio and hydraulic radius (0.53), slope and w/d ratio (0.50).