Rahman M.M.,Ministry of Water Resources |
Sarkar S.,Indian School of Mines |
Rai R.K.,DHI India Water and Environment Pvt. Ltd.
Journal of Hydrologic Engineering | Year: 2013
Bangladesh is a flood prone country where huge damages take place every year. Therefore, to minimize flood extremes, it is important to control the flood peaks at the upstream area through suitable watershed management practices. The flood control management at the watershed scale requires good quality flood data. However, in developing countries like Bangladesh, such hydrological information is rarely available at the watershed level. Under such circumstances, it is important to use a hydrological model representing the rainfall-runoff process to arrive at the extreme flows in the rivers, which require extreme rainfall data as a major inflow to the hydrologic system. Furthermore, the density of rain gauges in Bangladesh is low and the quality of available flood data is poor. Considering this, it is important to develop regional extreme rainfall maps for the reliable estimation of flood flows in the river by using a suitable modeling approach. Therefore, in the present paper, an attempt has been made to derive the regional best fit extreme rainfall pattern for Bangladesh for the estimation of extreme rainfall quantiles. This study uses the annual maximum daily rainfall of 68 rain gauge stations. An autocorrelation test isapplied to test the independency of the data. Later, considering the heterogeneity in the hydroclimatic and topographic details, entire rain gauge stations have been clustered into six hydroclimatically homogeneous regions; namely, northeast (NE), northwest (NW), southeast (SE), southwest (SW), coastal, and central regions, by using the k-mean clustering technique. The stations that did not pass the discordant and heterogeneity test were discarded from the regional frequency analysis. For regional frequency analysis, the L-moment method was applied. Based on the ZDIST goodness of fit test and the L-moment ratio diagram, the generalized extreme values distribution was identified as the best fit for the SE, NW, and coastal regions. However, for NE, central, SW regions, the best fit distributions were generalized logistic and generalized Pareto, respectively. Using the derived distributions, regional extreme rainfall quantiles were estimated, followed by geo-mapping in ArcGIS 9.2. © 2013 American Society of Civil Engineers.
Rath S.,DHI India Water and Environment Pvt. Ltd |
Nayak P.C.,National Institute of Hydrology |
Chatterjee C.,Indian Institute of Technology Kharagpur
International Journal of River Basin Management | Year: 2013
The current study employs a hierarchical adaptive network-based fuzzy inference system for flood forecasting by developing a rainfall-runoff model for the Narmada basin in India. A hybrid learning algorithm, which combines the least-square method and a back propagation algorithm, is used to identify the parameters of the network. A subtractive clustering algorithm is used for input space partitioning in the fuzzy and neurofuzzy models. The model architectures are trained incrementally each time step and different models are developed to predict one-step and multi-step ahead forecasts. The number of input variables is determined using a standard statistical method. An artificial neural network (ANN) model which uses an Levenberg-Marquardt (LM) backpropagation training algorithm has been developed for the same basin. The results of this study indicate that the hierarchical neurofuzzy model performs better compared to an ANN and the standard fuzzy model in estimating hydrograph characteristics, especially at longer forecast time horizons. © 2013 Copyright International Association for Hydro-Environment Engineering and Research.
Paliwal R.,DHI India Water and Environment Pvt. Ltd. |
Patra R.R.,DHI India Water and Environment Pvt. Ltd.
Water Science and Technology | Year: 2011
This study aims at analysing the impact of wastewater load of industrial units in Haldia on the water quality of the Hoogly estuary using numerical modelling techniques. Modelling was never attempted in this region because it was generally felt that simulating such a complex system would not be easy with limited data availability but MIKE 21, a hydrodynamic and water quality model, was used to simulate BOD and DO profiles in the study area and simulation provided reasonably good predictions. A scenario assessment was also carried by increasing the flows from various sources to understand the site-specific relationships between pollution sources and water quality conditions and also to calculate the assimilative capacity of Hoogly with respect to waste discharged from the industrial units at Haldia. The results suggested that water quality of the canal towards closed Oil Jetty was highly deteriorated due to stagnant pond condition and discharges from a refinery. But large part of the canal was found to be well drained under tidal influence as a consequence of which both DO and BOD conform to the prescribed water quality standards most of the times. The impact of industrial waste load on the Hoogly was found to be negligible and the radius of influence was limited to about 200-300m across the estuary and about 1.6km along the shore during ebb conditions. Assimilative capacity of the region was estimated to be 837 kg/d as against the present load of 121 kg/d. The study suggested that the estuary had good dilution capacity and intense tidal mixing helped in rapidly diluting the pollutants. © IWA Publishing 2011.
Sarkar S.,North Eastern Regional Institute of Science and Technology |
Rai R.K.,DHI India Water and Environment Pvt Ltd
Water Resources Management | Year: 2011
Flood inundation extent is highly dependent on intensive rainfall and topography of floodplain. This paper presents a study to develop a flood inundation model for partially gauged upper Ganga catchment. For design flood computations, 100-year return period of 1 h duration rainfall is adopted. This is obtained by intensity duration frequency (IDF) relationship based on Self Recording Rain Gauge (SRRG) data of the study area. The SCS-CN method is used for rainfall excess computations. The Nakagami-m distribution has been used to compute Geomorphological Instantaneous Unit Hydrograph (GIUH) of different sub-catchments of upper Ganga river system because of non-availability of observed hydrograph. Routing of the hydrograph has been done by the Kinematic Wave (KW) approach. KW equations have been solved through Preissmann implicit method. The most sensitive KW parameters (i. e. overland roughness and channel roughness) have been estimated for a stretch on river Bhagirathi, a tributary of river Ganga. Nakagami-m distribution based GIUHs have been fed at the upper (i. e. input to the proposed model) as well as at downstream point (i. e. output to the proposed model) of that river stretch. Consequently, KW parameters have been calibrated by comparing the computed hydrograph with output hydrograph. Validation of estimated KW parameters has been carried out in the catchment of river Alaknanda which is another significant tributary of river Ganga. Thereafter, adopted KW parameters have been applied to calculate the design flood peak at the outlet of study area i. e. downstream of Haridwar city. Computations of overtopping water above the natural levees downstream of Haridwar city have been carried out considering the levee as broad crested weir. Topographic features of the floodplain have been obtained from freely available Shuttle Radar Topography Mission (SRTM) data. Finally, extents of submerged areas in different flood hours corresponding to design rainfall have been developed by ArcGIS 9.2 software. © 2011 Springer Science+Business Media B.V.
Rai R.K.,DHI India Water and Environment Pvt. Ltd. |
Upadhyay A.,DHI India Water and Environment Pvt. Ltd. |
Singh V.P.,Texas A&M University
Journal of Hydrology | Year: 2010
Overland roughness is one of the key parameters in hydraulic modeling of watershed runoff. During the evolution of a runoff hydrograph the flow roughness is not constant. Hypothesizing a nonlinear relation between surface roughness and flow depth, this study incorporates variable roughness in a kinematic wave (KW) model and investigates its effect on runoff from four watersheds of varying sizes and hydroclimatic conditions. The hydrographs yielded by the KW model with varying overland roughness were in satisfactory agreement with observed runoff hydrographs and the hydrograph shape was well preserved. To quantify the effect of variable roughness on runoff, the hydrographs generated by the KW model with variable roughness were compared with those generated with constant overland roughness. Based on the study, it was observed that hydrograph shape is, in general, better preserved in case of variable roughness than the constant roughness. © 2009 Elsevier B.V. All rights reserved.
Paliwal R.,DHI India Water and Environment Pvt. Ltd |
Srivastava L.,TERI University
Journal of Environmental Planning and Management | Year: 2012
This paper examines the effectiveness of EIA procedures in India in terms of the follow-up process. It provides an insight into the legal framework, roles and responsibilities of various stakeholders and the focus of Terms of Reference (TOR) provided for the follow-up. A 'practice analysis' was carried out to assess actual enforcement and implementation of environmental stipulations, based on information derived from the official records of regulatory authorities for the industrial estate of Haldia. The analysis was further substantiated through discussions with various stakeholders and personal observations. Several inadequacies were observed during the implementation of the process, in terms of ambiguous conditions, ineffective measures to ensure compliance, vested interests of industrial units, lack of co-ordination and inadequate resources available with implementing agencies. In order to ascertain effective follow-up practice, integrated efforts, i.e. focused and elaborated Terms of Reference (TOR), better monitoring support, extended legal powers, co-ordination among regulators for timely action, self-regulation among proponents and the involvement of local people, are essential. © 2012 Copyright Taylor and Francis Group, LLC.