1. River siltation, its impact and Way Forward

2. Introduction
Rivers are natural channels to drain water from highlands to lowlands/seas. Over the time, the high lands of an area are worn down. The material thus eroded is utilized further downstream to builds banks and lands. As the river flows from high gradient to low gradient, its stream power is lost proportionately, inducing thereby silt deposition en route. The river thus may be likened to conveyance system
Siltation process is subjected to several factors including physiography, geology. Meteorology, hydrology and flow characteristics of the particular reach.
Landslides, Climatic factors, land use pattern are important in inducing slope instability, such as fragile nature of rocks, active nature of tectonics in plate margins along with climatic factors.

3. Its Impact In Stream Impacts
Biological impacts e.g. turbidity, sedimentation, reduced productivity and species diversity.
Recreational impacts e.g. restriction of swimming, boating, fishing and reduction of overall aesthethics.
Sedimentation of channels and water storage bodies e.g reserviours sedimentation, impairment of navigation, siltation of training structures.
Increased abrasion of hydraulic equipment e.g HEP turbines.
River Morphological changes e.g. Shifting of river course, aggradations / degradation
Sand/Gravel Minning.( +ve Impact)

4. Off Stream impacts
Flood damage e.g. aggradation, increased damage from muddy water. (This may either be beneficial or may create serious problems depending on its nature, quantity and quality.)
Sedimentation of conveyance system e.g. Irrigation and drainage channels.
Increased cost of water treatment e.g. increased sedimentation times, clogging of filters.
Impairment of Industrial water use e.g.reduced cooling efficiency, abrasion of pumps and turbines.
Sealing of Irrigated soils.

5. Remedial Measures
The method of minimizing siltation may be of two folds- one that is required in the catchment and the other in the river itself.
(a) The method to be adopted in catchment may include-
An effective and permanent method of sediment control is soil conservation in the catchment which includes the following practices;
Afforestation and forest management
Regrading and grassland management
Cultivation practices, such as crop rotation, increasing organic matter, mulching, seasonal cover crops, contour cultivation, strip cropping and terracing.
Gully control and check dams- contour bunding and trenching.

6. (b) The method to be adopted in river itself-
Storage Reservoirs
Desilting basins.
River training works such as bank protection, spurs etc.
River training works for local sediment control e.g Sumerged vanes, bed bars, Bundalling etc.
Desilting- There are different methods of desilting such as flushing, slucing, siphoning, dozing, dredging etc.

7. Committee to study the problems of silting in rivers (Mittal committee).
Ministry of Water Resources, Govt. of India in the year 2001 constituted a Committee under the chairmanship of Dr. B.K. Mittal, former Chairman, Central Water Commission to study and report on the problem of silting in rivers and related aspects including feasibility of desilting.
Committee studied the siltation pattern in a few rivers in India and concluded that siltation is not pronounced and alarming.

8. It was suggested by the committee that desilting in general is not feasible technically, due to several reasons like non-sustainability, non-availability of vast land required for the disposal of dredged material etc. Dredging in general should not be resorted particularly in major rivers. There are, of course, some locations such as tidal rivers, confluence points with narrow constrictions and the likes which can be tackled by desilting after thorough examination and techno-economic justification. Desilting of rivers can marginally minimize the magnitude of floods and be effective only for a short period. This cannot be viewed in isolation of other approaches to manage floods. Committee was an opinion that desilting of rivers for flood control is not an economically viable solution. Desilting of rivers in vulnerable reaches may be suggested based on model study if it is found techno-economic viable. For navigation purpose the river reaches in the waterway path may be dredged to have minimum depth of water.

9. Points need to be discussed-
Efficacy of dredging as silt control measure for reducing flood levels
Possible solutions for neutralizing the aggradation tendency of the rivers and how best to provide relief from the ill effects of the silting trouble.
Comparision of sediment dredging with river training devices, both of which are helpful to deepen the river bed.
For minimizing the silt trouble in rivers, the precautions to be taken in designing of hydraulic structures.

10. MORPHOLOGICAL STUDIES OF 15 RIVER USING REMOTE SENSING TECHNOLOGY
Thank You

11. Dynamics of flow and sediment transport are the principal elements.
River Morphology
Morphology (of river) is a field of science which deals with the change of river plan form and cross sections due to sedimentation and erosion.
Dynamics of flow and sediment transport are the principal elements.

12. Importance of Morphological studies
The Morphological Studies play an important role in knowing the Nature of rivers which helps in planning, designing and maintaining of Flood Protection/ river training Works and water resources projects.
The morphological studies help in finding the vulnerable spots for
(a) Bank Erosion
(b) Deposition
(c) River Bed Aggradation
(d) River Bed Degradation

13. Morphological studies in 12 th Plan
In 12th Plan, Rs Crore has been approved by the EFC for Morphological Studies under Plan Scheme “R&D Programme in Water Sector”.
Study is taken up by CWC through consultancy to IITs/NIT on nomination basis.
Work has been awarded after approval of MoWR.

14. CONSULTANCY AWARDED FOR MORPHOLOGICAL STUDIES
Sl. No.
Institute
River Basin
Cost (Rs.) 1.
IIT Roorkee
Ganga, Sharda, Rapti (3)
2,28,50,000 2.
IIT Delhi
Kosi, Bagmati, Yamuna (3)
1,94,38, 280 3.
IIT Guwahati
Bramhaputra, Subansiri, Pagladiya (3)
1,55,97,663 4.
IIT Madras
Krishna, Tungbhadra (2)
96,46,000 5.
IIT Kharagpur
Mahananda, Mahanadi, Hoogly (3)
1,46,46,268 6.
SVNIT Surat
Tapi (1)
72,85,538
Total
8,94,63,749
Say 8.95 Cr.

15. Works Involved
Remote sensing Techniques are capable of providing large information about river migration, changes in river course, land use changes etc with time.
The main objective is to study the shifting of river course and also changes in its Plan 10 years from the base year 1970 till 2010 using Remote sensing technology.

16. Works Involved Compile river drainage map in GIS.
Collect required information on major flood protection structures, existing water resources projects, important cities/ towns, CWC H.O sites, airport, island etc., and to be integrated with final river drainage maps.
All the data / layers will be compatible with India-WRIS portal and will be put on India-WRIS system.
Compile Changes in Land Use/Land cover and study of its impact on river Morphology.
Work out the rate of bank erosion/deposition in term of erosion length & erosion area w.r.t. base year at 50 km interval.

17. Works Involved
Evaluate the impacts of major hydraulic structures on morphological behaviour of river course and its impacts on river morphology.
Study of impact of changes in annual rainfall in the basin on river morphology.
Identify critical and other vulnerable reaches, locations. Analysis of respective rate of river course shifting and based on it, future predication of river course behaviours.
Suggest suitable river training works for restoration of critical reaches depending on site conditions.

18. Details of Milestones Mile Stone Time Percent Payment
Mobilisation of resources, procurement of input data etc.
In advance after signing of MoU
30% of total cost (excluding the input data cost) + 100% of input data cost on actual basis*
Inception Report
3 months
NIL
Interim Report
9 months
30% of total consultancy charges excluding input data cost
Draft Final Report
1 year 9 months
30% of total consultancy charges excluding input data cost
Organisation of Dissemination Workshop
1 year 10 months
Payment released at the stage of Draft Final Report will take care of this expenditure
Final Report
2 Years
10% of total consultancy charges excluding input data cost

19. STATUS OF CONSULTANCY WORKS OF MORPHOLOGICAL STUDIES
Work awarded for all studies.
MOU has been signed with all IITs/SVNIT
Inception Report submitted by
(a) SVNIT Surat for River Tapi
(b) IIT Roorkee for river Ganga, Sharda & Rapti
(c) IIT Delhi for river Kosi, Bagmati & Yamuna
Interim Report submitted by
(a) IIT Roorkee for river Ganga, Sharda & Rapti
(b) IIT Delhi for river Kosi, Bagmati & Yamuna