Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Vishwas S. Kale ¹

Affiliations
1 Department of Geography, University of Pune, Pune 411007, IN

Abstract

In the present study, the temporal patterns of monsoon floods on five large rivers of the Deccan Peninsula have been investigated. Analyses of the long-term annual maximum discharge/stage data, available for the last 100 years or so, show non-random behaviour in terms of distinct periods of high and low floods. The normalized accumulated departure from mean (NADM) plotting method has been used to identify great periods of below-average (low) and above-average (high) floods. Examination of the data reveals lower frequency and magnitude of large floods during the late-1800 and early-1900 period, and a period of increased frequency of large floods between 1940s and 1960s. The results of the investigation also indicate that the high (low) flood response is consistent with increased (decreased) precipitation in the basins. There is a clear evidence of an enhancement in the magnitude and frequency of large floods in the post-1940 period.

Keywords

Flood Studies, Monsoon Rainfall, High/low Flood Periods, Climatic Changes, Deccan Peninsula.

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Vishwas S. Kale ¹, S. N. Rajaguru ²

Affiliations
1 Department of Geography, University of Poona, Pune- 7, IN
2 Department of Archaeology, Deccan College, Pune-6, IN

Abstract

A detailed micro-level statistical analysis has brought out the spatial variation in the terrain of Pravara and Mula sub-basins. Principal component analysis has aided in establishing three groups of inter-related variables; and the Factor Analysis has been able to synthesize patterns of six geomorphic variables into a single comprehensive pattern labelled as 'Morphogenetic Regions'. The multivariate analysis has been able to derive equations of high predictive and descriptive value. Such an approach to terrain analysis has been found to be very fruitful than the conventional morphometric analysis.

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Vishwas S. Kale ¹

Affiliations
1 Department of Geography, University of Pune, Pune-411 007, IN

Abstract

This paper provides a brief outline of the flood studies in India in the field of geomorphology, meteorology and hydrology. The review clearly shows that, though the general characteristics of floods have been known for a long time, our scientific understanding of the floods remains incomplete to a surprisingly large extent. Existing studies seem to concentrate in two areas. The first deals with hydrometeorological analysis of flood producing rainfall and associated synoptic conditions. The second area is related to streamflow analysis and the estimation of design floods. Both the research areas place considerable emphasis on statistical analysis and modelling. This trend is likely to continue in future. While a quantitative approach to the problem is indispensable in predictive models, it is felt that future opportunities to improve our understanding of this recurring natural hazard should include research into the natural trends and the behaviour of floods on longer time scale, and increased evaluation ofthe impact of anthropogenic activities on the river systems.

Keywords

Flood Geomorphology, India, Hydrology, Cyclonic Storms, Human Activity.

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Vishwas S. Kale ¹, Sheila Mishra ², Victor R. Baker ³

Affiliations
1 Department of Geography, University of Pune, Pune 411 007, IN
2 Department of Archaeology, Deccan College, Pune 411 006, IN
3 Department of Hydrology and Water Resources, University of Arizona, Tucson AZ 85721, US

Abstract

A continuous record of the largest Narmada floods over the last 2000 years was obtained from Sakarghat, on the Narmada River from a study of slackwater flood deposits. Two sequences of extreme floods date between ca. 400 and 1000 AD and post-1900 AD. The period, 400-1000 AD representing a period of less frequent but more extreme floods, has been documented in the archaeological record as one of decline of human settlements.

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Vishwas S. Kale ¹

Affiliations
1 Department of Geography, University of Pune, Pune - 411 007, IN

Abstract

The recent Kosi megaflood, caused by a breach in the Kosi embankment in Nepal on August 18, 2008 and a sudden change in the course of the Kosi River, was one of the most significant and damaging flood events ever to hit Bihar. The Kosi disaster also ranks as one of the greatest disasters in India. This preliminary note briefly discusses some of the available details of the megaflood, the past great floods on the river, the special hydro-geomorphic characteristics of the basin, and the probable reasons for the failure of structural measures designed to mitigate the flooding problems on this Himalayan river with unique behavioural characteristics.

Keywords

Kosi River, Hydrogeomorphic Characteristics, Catastropic Floods, North Bihar.

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Vishwas S. Kale ¹

Affiliations
1 Department of Geography, Univ. of Pune, Pune - 411 007, IN

Abstract

No Abstract.

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Vishwas S. Kale ¹, Nikhil Shejwalkar ¹

Affiliations
1 Department of Geography, University of Pune, Pune - 41 1 007, IN

Abstract

In this paper some observations have been made on the current paradigm of long-Distance paral1el retreat of great escarpments. The paper examines selected aspects of river and basin morphometry in the western Deccan Basalt Province (DBP) to get a better insight into the style and rate of Western Ghat evolution. Various drainage basin morphological attributes were extracted from digital elevation model (DEM) constructed by using the ca 90 m resolution Shuttle Radar Topographic Mission (SRTM) digital elevation data. The main findings that emerge from the analyses of the long profiles, basin shapes, length-area and slope-area relationships and escarpment sinuosity are (I) there is a remarkable similarity in the shapes of the long profiles of the principal coastal rivers suggesting that the headward erosion and growth of the drainage in the Ghat zone has proceeded, more or less, uniformly, and the geomorphic or geologic conditions have not favoured any particular river, (11) the coastal basins are more circular than expected, indicating that there is a tendency to increase the basin area laterally via tributaries, rather than longitudinally, and that the tributaries have also played a crucial role in the recession of the escarpment, (111) the Konkan rivers are characterized by severe deepening in the upper-medial portion and dominance of fluvial processes in the headwater reaches, and (IV) the Ghat Escarpment sinuosity is relatively low, but not very distinct from the sinuosity of the basin divides on the Maharashtra Plateau, implying that the geomorphic processes that create and sustain steep slopes along the western continental margin and over the Maharashtra Plateau are fundamentally same. All the geomorphic evrdences suggest that the tempo of Ghat Escarpment retreat is modest at best, and it seems that the Ghat scarp has receded maximum by a few kilometers.

Keywords

Western Ghat, Escarpment Evolution, Morphometry, SRTM-DEM, Parallel Retreat, Downwearing.

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Vishwas S. Kale , Ken J. Gregory , Veena U. Joshi

Abstract

No Abstract.

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Vishwas S. Kale ¹, Avijit Gupta ², Ashok K. Singhvi ³

Affiliations
1 Department of Geography, University of Pune, Pune - 41 1 007, IN
2 School of Geography, University of Leeds Leeds, LS2 9JT, GB
3 Physical Research Laboratory, Ahmedabad 380 009, IN

Abstract

No Abstract.

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Vishwas S. Kale ¹, veena U. Joshi ², Pramodkumar S. Hire ³

Affiliations
1 Department of Geography, University of Pune, Pune - 41 1 007, IN
2 Department of Geography, S P College, Pune - 411 030, IN
3 Department of Geography, HPT/RYK College, Nashik - 422 005, IN

Abstract

The Pleistocene-Holocene palaeohydrological and palaeoenvironmental conditions of the Deccan Trap rivers are not Well-Established. This is mainly on account of the limited extent of alluvial deposits and scarcity of palaeochannels to estimate former river discharges. This paper reports the results of recent investigations it a palaeochannel and the Volcanic-Ash associated alluvial materials at two sites located in the Semi-Arid parts of the Deccan Trap region. The palaeochannel is preserved in, and defined, by the volcanic ash. The ash is believed to be associated with the 74 ka Toba Mega-Eruption.

The geometry of the palaeo and modern channels were determined by undertaking EDM surveys. The mean, maximum and bankfull discharges of the palaeo and modern channels were estimated on the basis of published relationships between discharge and channel dimensions. The estimates indicate a bankfull discharge of about 15-40 m³s¹ for the palaeochannel and between 600 and 900 m³s¹for the modern channel. The estimates suggest that modern discharges are higher by about one order of magnitude.Stratigraphical studies at the sites show that the ash layer is often associated with thick black clays, referred to as fissured clays, which belong to marine isotope stage 3 andior 4 On the basis of modern analogs it was inferred that the Ash-Associated fissured clays represent sediments of seasonal, Low-Energy wetlands. The sedimentological characteristics indicate that during and after the Toba event the monsoonal climate was drier and river discharges were depleted. This inference is also supported by estimated mean and maximum discharges passing through the Kukadi Palaeochannel. We infer that at the time of the Toba event, which occurred during marine isotope stage 5-4 transition, the monsoon discharge and rainfall were much lower than the present in the Deccan Trap region.

Keywords

Palaeochannel, Fissured Clays, Palaeohydrology, Palaeoclimate, Deccan Traps.

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Vishwas S. kale ¹, Victor R. Baker ²

Affiliations
1 Department of Geography, University of Pune, Pune 411 007, IN
2 Department of Geosciences, University of Arizona, Tucson, AZ 85721, US

Abstract

Fluvial archives include slackwater flood deposits (SWD), which not only preserve informatron about centennia to millennial-scale changes in the flood regime conditions, but also provide information on climate vanability and extreme climatic events The present study is based on SWD evidence from six large rivers in central and western Indla A remarkable feature that has emerged From the palaeoflood analyses is that the evidence of large floods between circa 14^thand 19^th century AD is generally missing. Considering the manner in which the rivers build the palaeoflood sequences in stable bedrock gorges, the striking and conspicuous absence of flood deposits of this period indicates a significantly reduced frequency of large floods Since modern floods on these rivers are the result of severe cyclonic storms, the absence of large palaeofloods not only implies a sharp decline in the frequency of flood-producing severe cyclonic systems, but also an overall decrease In the summer monsoon intensity Interestingly, this period of less frequent large floods (ca 14^th-19^th century AD) approximately coincides with the Little Ice Age (1300 to 1850 AD), which was characterized by relatively cool and dry conditions, and a weakening of the Indian summer monsoon.

Keywords

Palaeofloods, Slackwater deposits, Extreme climatic events, Monsoon intensity, Little Ice Age.

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Vishwas S. Kale ¹

Affiliations
1 Department of Geography, University of Pune, Pune-411007, IN

Abstract

Flooding m monsoon-fed rivers profoundly challenges flood hazard management because of large spatio-temporal variability m the monsoon rainfall over the Indian region and scarcity of long-term hydrological data Under such circumstances, pre-instrumental (recent, historic or pre-historic) records of large floods could be reconstructed by using palaeoflood hydrological techniques This paper briefly describes the methodology adopted to reconstruct longterm flood chronologies (over centuries to millennia) using geological and geomorphological evidence, and summarizes the results of palaeoflood studies on eight Indian nvers undertaken during the last two decades The paper also briefly discusses the potential for palaeoflood hydrological studies in different hydro-geomorphic regions of India and the future prospects of palaeoflood hydrological investigations in India for flood-risk assessment of both gauged and ungauged nvers Three conclusions are possible concerning palaeoflood archives m India (a) the palaeoflood records generally span a time period of 1-2 millennia, (b) the post-1950 floods were observed to be the largest at least dunng the last several hundred years, indicating increase in both the magnitude and frequency of large floods m recent decades, and (c) the period between ca W and 19'' century AD was marked by a sharp decline in the frequency of large-magnitude floods on all rivers, suggesting a palaeochmatologic cause This distinct period of low monsoon floods approximately coincides with the Little Ice Age, a global climatic phenomenon In a country like India, where there is paucity of long-term hydrological data, palaeoflood records are a great source of potential information that could play a critical role in formulating design decisions for different types of engineering projects as well as water resource development projects on both ungauged as well as gauged rivers.

Keywords

Palaeofloods, Monsoon floods, Slackwater deposits, Regional palaeoflood analysis, Little Ice Age.

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Vishwas S. Kale ¹

Affiliations
1 University of Pune, Pune, IN

Abstract

No Abstract.

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Vishwas S. Kale ¹

Affiliations
1 Department of Geography University of Pune, Pune 411 007, IN

Abstract

Although the definitions of tropics vary amongst disciplines (Seidel et al. 2008), the tropics are traditionally defined as the area approximately between 30° N and S latitude. This low-latitude region, covering over half of the total surface area of Earth, is characterized by rich diversity of landforms including high mountains and plateaus, mighty rivers, deep weathering profiles, ancient erosional surfaces, mega deserts, large deltas and alluvial fans, extensive alluvial plains and wetlands. Some of the greatest rivers in the world, ranked by magnitude of discharge and sediment load, are located in the tropics.

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