Vikrant Jain

Derivation of Unit Hydrograph from GIUH Analysis for a Himalayan River

Unit Hydrograph (UH) is the most popular and widely used method for predicting flood hydrograph resulting from a known storm in a basin area. However, the non-availability of UH due to poor network of raingauge stations in flood prone Indian river basins is a major concern. The computation of Hortons ratios and their application in generating the Geomorphological Instantaneous Unit Hydrograph (GIUH) can provide a solution for ungauged rivers. A detailed drainage network analysis was carried out for a 5th order flood- prone Himalayan river system in order to highlight its significance in flood management program. The equations for GIUH of 5th order stream were derived through Markov Chain analysis. The GIUH model for the 5th order stream was used to derive the first ever analytical UH of the river. Further, it was applied to determine the 50-yr return period flood. The 50-yr return period flood matches with the result of flood frequency analysis based on observed peak discharge data. This drainage network analysis and application of GIUH can provide a significant contribution towards flood management program.

Where do floodplains begin? The role of total stream power and longitudinal profile form on floodplain initiation processes

Understanding downstream transitions in river character and behavior is a basic concept in fluvial geomorphology. Downstream patterns of depositional processes can be differentiated between channel and floodplain components. In this study a generic set of methods is used to analyze floodplain initiation and continuity in relation to downstream changes in total stream power (slope and discharge) and longitudinal profile form for river courses in the upper Hunter catchment, Australia. Absolute values of these controlling factors are shown to be poor indicators of threshold conditions at which floodplains begin to form along river courses. Catchment-scale patterns of stream power and the form of longitudinal profiles provide better predictors of this transitional zone. The total stream power plot derived along longitudinal profiles represented by a second-order exponential curve has a bimodal pattern. In most cases, floodplains begin to form in a transition zone characterized by a trough area within the bimodal stream power distribution. This bimodal stream power pattern provides a better means to identify this transition in depositional processes along longitudinal profiles than more conventional single peak stream power analyses based on first-order exponential longitudinal profiles. Indirect controls such as basin geology and accommodation space also influence the initiation and pattern of floodplains.

Geomorphological Manifestations of the Flood Hazard: A Remote Sensing Based Approach

Abstract Flood hazard is one of the most severe problems in the Himalayan river basins. Although floods are essentially hydrological phenomenon, the uneven distribution of floods in the river basin highlights the control of geomorphological and geological factors. A proper understanding of these factors is critical for a successful flood management programme. Remote sensing data is of immense value in evaluating the geomorphological and geological controls in flooding. The present paper highlights the control of geomorphology and neotectonics on flood hazard in north Bihar Plains, eastern India. The Indian Remote Sensing (IRS) data has been used and a variety of image processing techniques have been employed.

River Systems and River Science in India: Major Drivers and Challenges

Rivers and especially large rivers are one of the most important geomorphic systems, on which the sustainability of modern society is dependent. In spite of the pivotal role rivers play in sustaining human civilizations, the understanding of large river systems and appreciation of their multidimensional nature is still fragmentary. Further, almost all rivers on this globe have been ‘disturbed’ significantly due to prolonged human interference. Therefore, there is an urgent need to initiate an integrated effort to develop a process-based understanding of the large river systems. An integrated effort should be made towards developing a core of River Science that includes hydrology, hydraulics, fluvial and hill slope geomorphology, geochemistry, ecology, glaciology, climate change and interaction of these disciplines at different scales through physical and mathematical modelling. Several countries have recognized the need for adopting such a multi-disciplinary approach towards river science centered on hydrology-geomorphology-ecology linkages. Further, the sustainable management of rivers requires a further level of integration that uses the complementary expertise of scientists, engineers and planners.

The Dynamic Kosi River and Its Tributaries

The Kosi River is known as one of the most dynamic river systems. Even smaller interfan rivers joining the Kosi River at downstream reaches are also characterised by frequent channel migration. Avulsion process is responsible for dynamic nature of these rivers. An in-depth process understanding of such geomorphic processes is required to manage flood hazards along aggrading river systems. New conceptual advancement in geomorphic studies supported with significant enhancement in remote sensing and surveying techniques will help to develop future strategies for sustainable management of such dynamic rivers.

Estimation of snow and glacial melt contribution through stable isotopes and assessment of its impact on river morphology through stream power approach in two Himalayan river basins

The impact of increased temperature on the Third Pole, as the Himalayas is referred to, and the likely cascading impacts on the general downstream hydrology have been widely noted. However, the impact on fluvial geomorphology has not received specific attention. Change in the glacial domain in terms of melt increase will change discharge and sediment flux into fluvial system, which will induce changes in fluvial processes and forms. The present work attempts to study this process-based glacio-fluvial coupling in the two neighbouring glaciated river basins in the Northwest Himalaya, viz., the Sutlej and the Yamuna river basins till the mountain front. A total of 194 samples of river, tributary and groundwater of pre- and post-monsoon seasons in the two river basins were analysed for stable isotopes. The trend of δ18O and electrical conductivity along the mainstream gives qualitative idea on the influence of headwaters in the downstream of the catchment thereby allowing inference on melt contribution. Further, two component mixing model using stable oxygen isotope of two seasons water samples showed that melt contributes about 41.1–66.8 and 6.6–10.6% at different points to the total river discharge in the Sutlej and the Tons River (the glaciated, major tributary of the Yamuna River) basins, respectively. For different scenarios of increase in melt, stream power increase in the Sutlej River basin is significant as opposed to the Tons River. River channel in the Sutlej River basin will be significantly more impacted in comparison with the Yamuna River system.