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Rohni is a subwatershed of Dhasan river of Betwa river system. The Morphometric analysis of Rohni watershed was carried out by using remote sensing and GIS techniques and using ASTER data. Based on hierarchical rank five subwatersheds streams are identified which are represented by the dendritic to subdendritic drainage pattern. The drainage, density, slopes and relief maps were prepared. The corresponding trends of each watershed with Precambrian structures and mean bifurcation ratio (4.61) suggest that the drainage pattern is structurally controlled. The high value of Rho Coefficient is suggestive of high hydrologic storage during a flood and shows less effect of erosion. The low value of the form factor indicates that the basin is elongated and is less prone to flood. The circulatory ratio implies that the youth and mature stages are dominant in Rohni basin. The low drainage density (1.51) is indicative of the presence of less permeable soil with a low infiltration rate and less erosion exposure in the basin. The low ruggedness and Melton ruggedness values indicate that the terrain is smoother and moderately rugged and is less susceptible to soil erosion. The drainage orientation of Rohni watershed is represented by polymodal distribution (NE-SW, E-W and NW–SE). The NNW-SSE and NE-SW trending major lineaments are prominent in the study area. The trends of low orders streams (NE-SW, NNW-SSE) coinciding the trends of major lineaments are indicative of tectonic control. The ENE-WSW trending high order streams show major tectonic control.

Jamini a tributary of Betwa River has Jamrar, Onri, Sajnam, Shanzad and Baragl five subwatersheds. The quantitative morphometric analysis of its subwatersheds was carried out by using advanced techniques of remote sensing and GIS. The linear, areal and relief parameters along with hypsometric values were generated for each subwatershed of Jamini basin. The remotely sensed Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM) data with a capture resolution of 3.0 arc second and pixel resolution of 30 m were used to extract the drainage map, density, contour, aspect and other maps. The mean bifurcation ratio (3.79 to 5.04) of Jamini and its all subwatersheds indicate that the drainage is structurally controlled. The Rho coefficient values reveal that the higher hydrologic storage during the flood and a decrease in the erosion during elevated discharge are observed in the basin. The drainage density (1.0 to 1.04) indicates that the basin is impermeable and shows low groundwater storage capacity in hard rock granitic terrain. The form factor (0.18 to 0.49), elongation and circulatory ratios indicate that the Jamini basin and subwatersheds are significantly elongated and show low peak flow of longer duration. The values of Ruggedness and Melton ruggedness number infer that the basin is slightly rugged and less prone to erosion and sediment transport. The S-shaped hypsometric curves show that the basin is susceptible to moderate erosion and the hypsometric index values (0.49 to 0.50) imply that the basin has mature geomorphic terrain with moderately eroded landscapes.

Kelani River Basin in Sri Lanka experiences frequent flooding resulting in loss of lives and properties in this basin. Keeping this in view, a study is taken up for Flood Assessment in Kelani River Basin, Sri Lanka up to Hanwella gauging site using HEC-Hydrologic Modelling System (HEC-HMS) tool. In the study, various available options of HEC-HMS have been considered for evaluation using various goodness of fit criteria, such as NashSutcliffe model efficiency (NSE), Percent Error in Peak, and Percent Error in Time to Peak and Percent error in Discharge Volume (Volume Deviation (Dv)). The Basin model has been selected considering the Kelani river basin up to Hanwella gauging site as a single basin for simulation of flood hydrographs and, in eteorological model, the Gaged weight option, of HEC-HMS, is considered for rainfall analysis. For the transform model or direct runoff model, Clark UH, SCS UH and Snyder UH models are considered. The calibration (manual and automatic) and validation of model parameters are carried out using hourly rainfall-runoff data of the five storm events observed during the monsoon seasons of the years 2017, 2016, 2014 and 2012. The Arc Map-ArcGIS and HEC-GeoHMS have also been used to process the different types of spatial data required as input for the HEC-HMS model application. It is found that the Clark model is the best-suited model for flood assessment of Kelani River Basin. The calibrated and validated Clark model can be very much useful for water managers and decision-makers to adopt structural and non-structural measures to minimize the losses due to frequent occurrence of floods in Kelani River Basin.

The Bhagirathi River that originates from the snout of Gangotri Glacier at an elevation of about 4000 m is traditionally considered as the source of Ganga River. In June 2013, a multi-day cloudburst centred on the North Indian state of Uttarakhand caused devastating floods and landslides which resulted in massive loss of lives and property. This unusual rain event occurred during the tourist season in June, consequently trapping a large number of tourists and vendors in this area. Sudden release of stored water generated floods that created havoc downstream of most of the rivers in this area. This paper presents a description of the meteorological conditions which led to the catastrophic hydrological situation and flash flood as experienced in the large part of Bhagirathi basin in June 2013. The hydro-meteorological and discharge data for 14–18 June 2013 collected at an observatory near the snout of the Gangotri Glacier are analysed. This area normally receives less rainfall; the maximum monthly r...

Morphometric analysis forms the basis for planning water and soil conservation treatments in a watershed. Geospatial topology based morphometric analysis in Dholbaha watershed, located in the Kandi region of Punjab, was carried out using the IRS data of LISS IV, Cartoset-1 merged satellite data, ASTER DEM and ArcGIS-10.2 software. As per topology, Dholbaha watershed is the 5th order watershed. Out of all the 279 streams identified, 213 are of 1st order and one 5th order stream. The total stream length is found to be 191.73 kms. The dendritic drainage pattern is found with stream frequency of 4.67 no./km2 and mean bifurcation ratio of 3.9. Both length as well as number of streams decrease with the increase in the order of streams. Topological model indicates lesser effect of geological structure on the drainage pattern of the watershed. Drainage density of watershed (3.21 km/km2) reflects the closeness of spacing in channels with permeable sub strata. Fine drainage texture (7.34 no./km) and large length of the overland flow (150 m) in watershed resulted into high peaked hydrographs and high sheet erosion in the watershed. The circularity ratio, form factor and elongation ratio of the watershed 0.412, 0.51 and 0.72, respectively indicate that watershed is less elongated in shape, associated with medium to high relief, having moderately permeable sub-soil conditions resulting in moderate peak discharge, and moderate runoff volume resulting in high soil erosion. The watershed requires urgent conservation measures to control siltation of the reservoir.

Glacial hazards relate to hazards associated with glaciers and glacial lakes in high mountain areas and their impacts downstream. The climatic change/variability in recent decades has made considerable impacts on the glacier life cycle in the Himalayan region. As a result, many big glaciers melted, forming a large number of glacial lakes. Due to an increase in the rate at which ice and snow melted, the accumulation of water in these lakes started increasing. Sudden discharge of large volumes of water with debris from these lakes potentially causes glacial lake outburst floods (GLOFs) in valleys downstream. Outbursts from glacier lakes have repeatedly caused the loss of human lives as well as severe damage to local infrastructure. Monitoring of the glacial lakes and extent of GLOF impact along the downstream can be made quickly and precisely using remote sensing technique. A number of hydroelectric projects in India are being planned in the Himalayan regions. It has become necessary for the project planners and designers to account for the GLOF also along with the design flood for deciding the spillway capacity of projects. The present study deals with the estimation of GLOF for a river basin located in the Garwhal Himalaya, India. IRS LISSIII data of the years 2004, 2006 and 2008 have been used for glacial lake mapping, and a total of 91 lakes have been found in the year 2008, and out of these, 45 lakes are having area more than 0.01 km2. All the lakes have been investigated for vulnerability for potential bursting, and it was found that no lake is vulnerable from GLOF point of view. The area of biggest lake is 0.193, 0.199 and 0.203 km2 in the years 2004, 2006 and 2008, respectively. Although no lake is potentially hazardous, GLOF study has been carried out for the biggest lake using MIKE 11 software. A flood of 100-year return period has been considered in addition to GLOF. The flood peak at catchment outlet comes out to be 993.74, 1,184.0 and 1,295.58 cumec due to GLOF; 3,274.74, 3,465.0 and 3,576.58 cumec due to GLOF; and 100-year return flood together considering breach width of 40, 60 and 80 m, respectively.

Many of the major rivers in India originate from the Himalayas. These rivers have significant contribution from snow and ice which makes these rivers perennial. Due to steep slopes, all such streams have potential sites for hydropower generation. There is a requirement of estimation of the contribution from snow and glacier melt, rainfall contribution and sub surface contribution in the total runoff for sustainable supply of water to the hydropower plants. Considering this aspects, in this study a snowmelt runoff simulation model SNOWMOD suitable for Himalayan basins developed earlier has been modified and applied for simulation of flows. Input to the model such as glacier cover, permanent snow cover, seasonal snow cover generated through remote sensing techniques were used in conjunction with daily maximum and minimum temperature, rainfall and discharge. Two hydropower dam sites on major tributaries (Bhagirathi and DhauliGanga) of River Ganga have been selected for determination of different runoff components. However, though the data available was for a very limited period but the results indicate that these tributaries have significant contribution from snow and ice for long term sustainability of flows to these schemes.

The hydrological cycle, a fundamental component of climate is likely to be altered in important ways due to climate change. In this study, the historical daily runoff has been simulated for the Chenab River basin up to Salal gauging site using a simple conceptual snowmelt model (SNOWMOD). The model has been used to study the impact of plausible hypothetical scenarios of temperature and rainfall on the melt characteristics and daily runoff of the Chenab River basin. The average value of increase in snowmelt runoff for T + 1°C, T + 2°C and T + 3°C scenarios are obtained to be 10, 28 and 43%, respectively. Whereas, the average value of increase in total streamflow runoff for T + 1°C, T + 2°C and T + 3°C are obtained to be 7, 19 and 28%, respectively. Changes in rainfall by −10 and + 10% vary the average annual snowmelt runoff over the T + 2°C scenario by −1% and + 1% only. The result shows that melt is much more sensitive to increase in temperature than to rainfall.

A geomorphological instantaneous unit hydrograph (GIUH) is derived from the geomorphological characteristics of a catchment and it is related to the parameters of the Clark instantaneous unit hydrograph (IUH) model as well as the Nash IUH model for deriving its complete shape. The developed GIUH based Clark and Nash models are applied for simulation of the direct surface run-off (DSRO) hydrographs for ten rainfall-runoff events of the Ajay catchment up to the Sarath gauging site of eastern India. The geomorphological characteristics of the Ajay catchment are evaluated using the GIS package, Integrated Land and Water Information System (ILWIS). The performances of the GIUH based Clark and Nash models in simulating the DSRO hydrographs are compared with the Clark IUH model option of HEC-1 package and the Nash IUH model, using some commonly used objective functions. The DSRO hydrographs are computed with reasonable accuracy by the GIUH based Clark and Nash models, which simulate the DSRO hydrographs of the catchment considering it to be ungauged. Inter comparison of the performances of the GIUH based Clark and Nash models shows that the DSRO hydrographs are estimated with comparable accuracy by both the models. Copyright © 2007 John Wiley & Sons, Ltd.

The average distribution of precipitation provides essential input for understanding the hydrological process. The role of complex topography in mountainous basins makes the spatial distribution of precipitation different than the plain areas. Besides the rugged topography, the Himalayan basins also face the problem of limited physical accessibility and data availability.

Runoff estimation is an important aspect of river basin planning, development and management. Geomorphological instantaneous unit hydrograph (GIUH) approach holds a great potential for estimation of runoff from ungauged basins because of its direct application to ungauged basins, without going for cumbersome procedure of regionalization. In this study, GIUH is derived from the geomorphological characteristics of a basin and it is related to the parameters of the Clark instantaneous unit hydrograph (IUH) model as well as Nash IUH model for deriving its complete shape. The developed GIUH based Clark and Nash models are applied for simulation of the direct surface runoff (DSRO) hydrographs for ten rainfall‐runoff events of the Ajay basin upto Sarath gauging site of eastern India. The geomorphological characteristics of the Ajay basin are evaluated using the GIS package, Integrated Land and Water Information System (ILWIS). A comparison of the performances of the GIUH based Clark and Nash models in s...

For estimation of runoff response of an ungauged catchment resulting from a rainfall event, geomorphologicalinstantaneous unit hydrograph (GIUH) approach is getting popularbecause of its direct application to an ungauged catchment. Itavoids adoption of tedious methods of regionalization of unithydrograph; wherein, the historical rainfall-runoff data of anumber of gauged catchments are required to be analyzed. In thisstudy, the GIUH derived from geomorphological characteristics ofa catchment has been related to the parameters of Clark IUH modelfor deriving its complete shape. The DSRO hydrographs estimatedby the GIUH based Clark model have been compared with the DSROhydrographs computed by the Clark IUH model option of the HEC-1package and the Nash IUH model by employing some of the commonlyused error functions. Sensitivity analysis of the GIUH basedClark model has been conducted with the objective to identify thegeomorphological and other model parameters which are moresensitive in estimation of peak of unit hydrographs computed bythe GIUH based Clark model. So that these parameters may beevaluated with more precision for accurate estimation of floodhydrographs for the ungauged catchments.

In the Himalayan region of India, most prospective sites for microhydro projects are ungauged and there are insignificant data for analysis. Design flow estimates are made using a regional flow-duration curve. Regional studies on Himalayan watersheds do not appear to have been reported in the literature. Therefore, models are developed for 1,200 ungauged watersheds of the Lower Himalayas. To this end, the region, comparatively larger in size than the catchment, is assumed to be hydrometeorologically homogeneous in its behavior. Formulation of models is based on data transfer between gauged watersheds of the same region, statistical normalization, and empirical regional relation. The performance of a specific model developed for Himachal Pradesh (Region C) is evaluated using the data of 13 watersheds in calibration and 4 watersheds in validation. It is found that the statistical approach of quantile estimation (nondimensional) performs satisfactorily in calibration as well as in validation. The simple powe...

The present study aims at developing regional flood formulae for the Krishna basin covering the parts of Karnataka and Maharashtra states. The study has been carried out using Index-flood, EV-I, GEV and Wakeby Distributions. The results indicate that Index-flood method and EV-I distribution yields better results in comparison with the other two methods used in predicting the flood at different sites in the basin.

The real time flood forecasting is one of the most effective nonstructural measures for flood management. For formulating the flood forecast in the real time, the observed meteorological and flow data are transmitted to the forecasting station through the different means of data communication which include telephone, wireless and network of telemetry stations etc. The collected meteorological and flow data in real time are then used into the calibrated & validated real time flood forecasting model to forecast the flood flow and corresponding water levels for different lead periods varying from few hours to few days depending on the size of catchment and purpose of the forecast. The structure of the model should be simple and it should not have excessive input requirements, but at the same time the forecasted flood must be as accurate as possible. Different types of real time flood forecasting techniques and models have been suggested and used by many investigators. These can be broadly classified into (i) deterministic models, (ii) stochastic and statistical models and more recently (iii) Artificial Neural Network (ANN) and fuzzy logic techniques. In India the various flood forecasting centers are using different forecasting models, based on the availability of hydrological and hydro-meteorological data, basin characteristic, computational facilities available at the forecasting stations, warning time required and purpose of forecast. Some of the commonly used methods by various forecasting stations include: (i) simple correlation based on stage-discharge data, (ii) co-axial correlation based on stage, discharge and rainfall data etc, (iii) net work model wherein the lateral flows from different sub-basins are calculated using unit hydrograph approach and successive routing through different sub-reaches is carried out using river flood routing techniques, and (iv) hydrologic models (at selected places). The recent techniques like ANN and fuzzy logic are being currently used by the academicians and researchers for the development and testing. In this lecture brief description of various real time flood forecasting models and techniques being used in India are presented. The limitations of the techniques are discussed. The status of the real time flood forecasting in India including those of the arid and semi-arid basins is presented. The present gaps in the application of real time flood forecasting techniques in India are highlighted. ________________________________________________________________________ * Scientist F, National Institute of Hydrology, Roorkee247 667, India

In this paper, flood problems in India, regional variability of the problem, present status of the ongoing management measures, their effectiveness and future needs in flood management are covered. Flood problems in India are presented by four zones of flooding, viz. (a) Brahmaputra River Basin, (b) Ganga River Basin, (c) North-West Rivers Basin, and (d) Central India and Deccan Rivers Basin. Some special problems, related to floods like dam break flow, and water logging in Tal areas, are also mentioned. Progress of various flood management measures, both structural and non-structural, are discussed. In addition, future needs to achieve efficient and successful flood management measures in India are also pointed out.