ISSN (Online) 2393-8021 ISSN (Print) 2394-1588 International Advanced Research Journal in Science, Engineering and Technology Vol. 2, Issue 10, October 2015 Copyright to IARJSET DOI 10.17148/IARJSET.2015.21025 116 Changing Character of Pool –Riffle Sequence: A Quantitative Representation of Long Profile of Ichamati, India Madhab Mondal 1 , Dr.L. N. Stapati 2 Assistant Teacher, Bhowanipur S. J. Institution, Hasnabad North 24 Parganas, W. B 1 Professor, Department of Geography, University of Calucutta, Kolkata, W. B 2 Abstract: The river Ichamati, which drains the eastern part of the district North 24 Pgs. W.B., India, has been analyzed regarding its long profile of the two years( 2004 and 2012) based on two windows. This paper has focused on the character of long profile such as, pool-riffle sequence and deviation index, which reveal the evolutionary tendency of long profile. Bed deformation technique (bdt) has identified the number and position of the pool and riffle on the riverbed. The classification of pool and riffle has been done with the help of tolerance value (T). The magnitude of T values is different in two windows. According to tolerance value (T), the position and number of pool and riffle has been changed significantly in two windows in two years. The threshold value of T has also been differed from 2004 to 2012. All these indicate the gradual decay of the river Ichamati. Keywords: windows, long profile, pool-riffle sequence, deviation index, evolutionary tendency, Bed deformation technique, tolerance value. 1. INTRODUCTION River management is not only merely a technical task but also inherently a socio-economic and cultural issue that reflect societal value (Higgs, 2003). In the last two decades, the management of rivers has become multifunctional procedure built upon a holistic base such as scientific knowledge, engineering interventions, control of pollution, water resource management, fisheries, transport, energy economy and protection of rivers (Lehotsky and Grešková, 2007). Rivers are the arteries of the landscape and also a geomorphologic processes create dynamic and diverse habitats, both in stream and in riparian and flood plain environments ( Dorava et al., 2001; Petts and Amoros, 1996 ), floodplain features are determinants of the diversity of habitat any given river ( Brierley, 2008 ). In modern sosirty there is a conflict between the dynamics of channel and human resource development with the outcome that many rivers and riparian environments have been significantly modified and damaged (Brookes and Shields, 1996). In the last two decades, the river management of has developed as a multifunctional procedure built upon a holistic based that unites the scientific knowledge, engineering interventions, control of pollution, water resource management, fisheries, transport, energy economy and protection of rivers. (Guneralp and Marston, 2012; Lehotsky and Grešková 2007). Ichamati is an irregular sinuous distributary channel, anthropologically delinked from the Padma- Mathabhanga- Churni system in early 1970s, making it a deranged, default and non-flowing water course ( Sarkar, 2004 ) and also a tidal creek that is classified as C type river ( Knighton, 1998 ). Longitudinal profiles of rivers are representative of watershed evolution, geologic structure, and sedimentary dynamics of the basin ( Costigan et al., 2014; Sinha and Parker, 1996; Leopold and Maddock 1953 ) and the slope of the stream along its axis, including stream characteristics such as knickpoints, riffles, pools, and Changes in vegetation, land use, surface geologic materials (soils, sediments, and rocks), slopes, and hydrology may be monitored to assess this vital sign (Lord et al., 2009 ), occur in response to both extrinsic and intrinsic controlling variables ( Schumm and Lichty, 1965 ). The long profile is influenced by the distribution of pools and rifles (Harmer and Clifford 2007; Anderson et al. 2005; Madej, 1999). Geomorphological research on pools and riffles has shown that theses bed forms are fundamental elements of meandering streams ( Krueger et al, 2007; Bhowmik and Demissie, 1982; keller and Melhorn, 1978; Wolman, 1955 ). The development of alternating deeps (pools) and shallows (riffles) are characteristic of both straight and meandering channel with heterogeneous bed materials in the size range of 2- 256 mm (Jackson and Beschta, 1984; Lisle, 1982 ) and pools are zones of convergent flow and scour, while riffles are zones of divergent flow and deposition ( Beschta and Platts, 1986; Clifford, 1983), The pool-riffle bedform sequence is a significant element in the dynamic adjustment between form and process in alluvial streams ( Clifford and Richards, 1992 ). Pools have been defined morphologically as topographic lows along a longitudinal stream profile ( O’Neil and Abrahams, 1984 ) and research have shown that they generally have asymmetrical cross sectional shape ( Frothingham et al, 2002; Knighton, 1981 ), develop within the broader context of stream behavior ( Knighton, 1998 ), different forms and secondary circulation occur in riffles