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1.
Change of river channel and bank erosion of the burhi dihing river (assam), assessed using remote sensing data and gis 总被引：1，自引：0，他引：1
The Burhi Dining river flows in a meandering course for about 220 km through alluvial plains of Assam including a short rocky
and hilly tract in between. Sequential changes in the position of banklines of the river due to consistent bank erosion have
been studied from Survey of India topographic maps of 1934 and 1972, and digital satellite data of 2001 and 2004 using GIS.
Two broad kinds of changes have been observed, e.g. alteration of direction of flow due to neck cut-off and progressive gradual
change of the meander bends that accounts for translational, lateral, rotational, extensional and other types of movement
of the meander bends. Study of bankline shift due to the bank erosion has been carried out for the periods 1934–1972, 1972–2001,
2001–2004 and 1934–2004 at 13 segments spaced at 5′ longitude interval (average 15 km) as the river course trends nearly east
to west. The amounts of the bank area lost due to erosion and gained due to sediment deposition are estimated separately.
The total area eroded in both banks during 1934–1972 was more (26.796 km2) as compared to sediment deposition (19.273 km2), whereas total sediment deposition was more (34.61 km2) during 1972-2001 as compared to erosion (23.152 km2). Erosion was again more in 2001–2004 (7.568 km2) as compared to sediment deposition (2.493 km2). During the entire period (1934–2004) of study the overall erosion on the both banks was 31.169 km2 and overall sediment deposition was 30.101 km2. The highest annual rates of bank erosion as well as bank building of the river are 21055.47 m2/km in 2001–2004 and 9665.81 m2/km in 1972-2001, respectively. Similarly the highest average annual rates of erosion as well as sediment deposition in both
banks are observed during 2001–2004 and 1972–2001, respectively. The hard rocks of the hilly tract situated in between result
in development of entrenched meandering and this tract has suffered minimum bank erosion. 相似文献
2.
Prediction and monitoring of monsoon intraseasonal oscillations over Indian monsoon region in an ensemble prediction system using CFSv2 总被引：1，自引：0，他引：1
S. Abhilash A. K. Sahai N. Borah R. Chattopadhyay S. Joseph S. Sharmila S. De B. N. Goswami Arun Kumar 《Climate Dynamics》2014,42(9-10):2801-2815
An ensemble prediction system (EPS) is devised for the extended range prediction (ERP) of monsoon intraseasonal oscillations (MISO) of Indian summer monsoon (ISM) using National Centers for Environmental Prediction Climate Forecast System model version 2 at T126 horizontal resolution. The EPS is formulated by generating 11 member ensembles through the perturbation of atmospheric initial conditions. The hindcast experiments were conducted at every 5-day interval for 45 days lead time starting from 16th May to 28th September during 2001–2012. The general simulation of ISM characteristics and the ERP skill of the proposed EPS at pentad mean scale are evaluated in the present study. Though the EPS underestimates both the mean and variability of ISM rainfall, it simulates the northward propagation of MISO reasonably well. It is found that the signal-to-noise ratio of the forecasted rainfall becomes unity by about 18 days. The potential predictability error of the forecasted rainfall saturates by about 25 days. Though useful deterministic forecasts could be generated up to 2nd pentad lead, significant correlations are found even up to 4th pentad lead. The skill in predicting large-scale MISO, which is assessed by comparing the predicted and observed MISO indices, is found to be ~17 days. It is noted that the prediction skill of actual rainfall is closely related to the prediction of large-scale MISO amplitude as well as the initial conditions related to the different phases of MISO. An analysis of categorical prediction skills reveals that break is more skillfully predicted, followed by active and then normal. The categorical probability skill scores suggest that useful probabilistic forecasts could be generated even up to 4th pentad lead. 相似文献
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Natural Hazards - Rainfall is the key climatic variable, on which water availability, food security and livelihood depend, especially in an agrarian society like the northeast region of India. It... 相似文献
4.
Statistical analysis of annual maximum rainfall in North-East India: an application of LH-moments 总被引：1，自引：1，他引：0
Surobhi Deka Munindra Borah Sarat Chandra Kakaty 《Theoretical and Applied Climatology》2011,104(1-2):111-122
An attempt has been made to determine the best fitting distribution to describe the annual series of maximum daily rainfall data for the period 1966 to 2007 of nine distantly located stations in North East India. The LH-moments of order zero (L) to order four (L4) are used to estimate the parameters of three extreme value distributions viz. generalized extreme value distribution (GEV), generalized logistic distribution (GLD), and generalized Pareto distribution (GPD). The performances of the distributions are assessed by evaluating the relative bias (RBIAS) and relative root mean square error (RRMSE) of quantile estimates through Monte Carlo simulations. Then, the boxplot is used to show the location of the median and the associated dispersion of the data. Finally, it can be revealed from the results of boxplots that zero level of LH-moments of the generalized Pareto distribution would be appropriate to the majority of the stations for describing the annual maximum rainfall series in North East India. 相似文献
5.
P. Kotoky M. K. Dutta R. Goswami G. C. Borah 《Journal of the Geological Society of India》2011,78(2):175-183
The bank sediments along the extremely meandered Dhansiri River channel, a south bank tributary of the mighty Brahmaputra
River, with erosion potentiality have been investigated to evaluate its certain geotechnical characteristics. The study has
shown that the bank sediments are basically composed of CL and ML types of soil. These types of sediments are very much prone
to liquefaction which in turn related to erosion susceptibility. The bank stability analysis has differentiated the studied
stretch into unstable, at risk and stable zones. Most of the erosion affected zones along the channel reach under study are
located within the unstable or at risk zones. The field study around Butalikhowa, Barguriagaon, Golaghat and Duchmuagaon areas
along the channel with active erosion activity has supported our contention and practical utility of the present study. It
is expected that such type of study will help in providing certain inevitable baseline information for various channel management
practices for this extremely flood prone areas of Northeast India. 相似文献
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Journal of Seismology - The North East (NE) of India is an earthquake (EQ) prone zone and has experienced considerable damages in the past due to high intensity EQs. With rapidly growing... 相似文献
9.
Changes in landuse and landcover along the Dhansiri River channel,Assam — A remote sensing and GIS approach 总被引：1，自引：0，他引：1
Information on landuse/landcover change is a critical input for natural resource management policy decisions. Remote sensing
data under GIS domain were utilized to evaluate the changes in land-use/land-cover (LU/LC) spanning a period of thirty three
years during 1975 to 2008 along the Dhansiri River channel, Assam, India. Seven different types of LU/LC were categorized
and out of them cropland was evident as the most important landuse/landcover practices followed by dense mixed jungle in 1975
and the settlement in 2008. Significant reduction (13.02%) in cropland area to settlement was observed. Moreover, teagarden
also occupies 0.77% of the total area from cropland and open mixed jungle. The changes in the areas of swampy land as evident
from the present study in turn will impact the environmental quality around it and will help to increase the surface run off
leading to enhancement of erosion processes. It is believed that the present study will help to contribute towards sustainable
land-use planning and management towards protection of extremely rich biodiversity of the North East India with mighty Brahmaputra
River system. 相似文献
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