AN INTRODUCTION TO THE HYDRAULIC AND TOPOGRAPHIC SINUOSITY INDEXES¹

Abstract

Stream sinuosity indexes are usually derived by dividing the length of a reach as measured along a channel by the length of a reach as measured along a valley. This method restricts stream sinuosity to those rivers which have downcut sufficiently to allow the formation of a floodplain. Therefore, all stream-occupied valleys in the youthful stage of erosion cannot provide a sinuosity value greater than unity, for during youth the valley and channel are coincident. It is an inherent flaw in existing indexes which suggests that all streams with a value of unity are straight, because in nature all streams have significant departures from a straight-line course and, hence, possess some degree of sinuosity. Consequently, one must assume that factors other than those which are purely hydraulic or lithologic must contribute to the sinuosity of all channels. These neglected factors are those which are topographic in origin. With this in mind, the author offers a set of indexes which takes into account both hydraulic and topographic sinuosity and which also is applicable to all streams in all portions of the cycle of erosion. HE significance of streams in the evolution T of landscapes has long fascinated geomorphologists, hydrologists, and geologists. A search of the early literature concerning streams reveals dominantly qualitative works, whereas more recent studies are characterized by quantitative and statistical methods. Part of the increased interest in quantitative inquiry results from the increased attention given to stream sinuosity. Unfortunately, most quantitative sinuosity studies restrict their measurements to hydraulic factors of channel behavior, often rendering themselves applicable only to streams whose valleys are beyond the early maturity stage of the cycle of erosion. In addition to the quantitative emphasis in recent decades has been the loss of clarity in some of the once rigidly defined qualitative terminology.It is not the purpose of this paper to condemn quantitative studies, or to escalate the significance of qualitative terminology. Rather, the author shall:

Detailed Hydrographic Feature Extraction from High-Resolution LiDAR Data

“…Two techniques for exploring relative horizontal accuracy and performing quantitative comparisons of such complex linear spatial features are presented. The first technique, relative sinuosity, is presented as a measure of the complexity or detail of a polyline network in comparison to a reference network (Leopold and Wolman, 1957;Friedkin, 1945;Schumm, 1963;Leopold et al, 1964;Müller, 1968;Chorley et al, 1984;Begin, 1985).…”

“…A variety of sinuosity indices have been proposed in connection with river 21 channel assessments and comparisons (Leopold and Wolman, 1957;Friedkin, 1945;Schumm, 1963;Leopold et al, 1964;Müller, 1968;Chorley et al, 1984;Begin, 1985).…”

Evaluation of morphometric parameters derived from Cartosat-1 DEM using remote sensing and GIS techniques for Budigere Amanikere watershed, Dakshina Pinakini Basin, Karnataka, India

“…Drainage basin is a basic unit in morphometric investigation because all the hydrologic and geomorphic processes occur within the watershed where denudational and aggradational processes are most explicitly manifested and is indicated by various morphometric studies (Horton 1945;Strahler 1952Strahler , 1964Muller 1968;Shreve 1969;Evans 1972Evans , 1984Chorley et al 1984;Merritts and Vincent 1989;Ohmori 1993;Cox 1994;Oguchi 1997;Burrough and McDonnell 1998;Hurtrez et al 1999). Morphometry is the measurement and mathematical analysis of the configuration of the earth's surface, shape, and dimension of its landforms (Agarwal 1998;Obi Reddy et al 2002;Clarke 1996).…”

Geomorphological Analysis and Hydrological Potential Zone of Baira River Watershed, Churah in Chamba District of Himachal Pradesh, India

“…Earlier, it has been well attempted by various hydrologists, geologists and geomorphologists. (Horton, 1932;Horton, 1945;Potter, 1957;Schumm, 1956;Mueller, 1968;Sutherland & Bryan, 1991;Rahmat & Mutolib, 2016) Morphometry is potentially a most important approach to geomorphology, since it affords quantitative information on large scale fluvial landforms, which make up the vast majority of earth configuration.…”