This presentation is the part of 12-day (28 January–8 February 2019) training workshop on “Multi-scale Integrated River Basin Management (IRBM) from the Hindu Kush Himalayan Perspective” organized by the Strengthening Water Resources Management in Afghanistan (SWaRMA) Initiative of the International Centre for Integrated Mountain Development (ICIMOD), and targeted at participants from Afghanistan.

1. Strengthening Water Resources Management in Afghanistan (SWaRMA)
Sedimentation Management (including Landslide and River bank Erosion)
Keshar Man Sthapit
keshar.sthapit@gmail.com

2. Household Irrigation
Hydro-power
Industry
Forestry
River Transportation
Multi Stakeholder of Water Resource!
Livestock
Tourism
Holistic Management of Water Management is essential
in fulfilling Water needs of Multi Stakeholders!

3. Watershed Area:
Dominated by Detachment Zone
Valley Area:
Dominated by Transportation Zone
Plain Area:
Dominated by Depositional Zone
Understanding
Upstream – Downstream Linkage

4. Upstream and Downstream Linkage in Small Scale (Landslide):
Upstream/Valley/Valley
Contributing Area Dominated
by Detachment Zone
Valley Area Dominated by
Transportation Zone
Downstream Area Dominated
by Depositional Zone

5. Nature’s law
• Water erosion at high elevation and sedimentation at low elevation
• Watershed degradation produce sediment, transported through valley and
deposit downstream.
• Sediment and runoff are the energy of the river writing its own course.
• Sediment load Reduces River capacity to accommodate the runoff thus cause
the flooding, and
• Sediment Deposition Makes the river shift and meander
• to distribute the sediment downstream and accommodate runoff.Why do you think the river shift and meander?

6. Reason for Shifting of Koshi River
Annual Sediment = 128 million cu. m.
Annual Av. Runoff = 52,700 million cu. m.
Observed at Chatara in Nepal
Koshi Basin in Nepal
1300 sq. km in Nepal
7800 sq. km
in India
Displaced 6.5 million population
(H.C, Reiger, 1976)
Koshi River Shifted 110
Kilometers from East to West
from 1731 to 1975

7. What we do in the Afghan watershed?

8. What we do in the Watershed will have downstream impacts!

9. Guiding Principles of Sediment Management
• Therefore,
Sedimentation management plays important role in the integrated
river basin management.
• Three Guiding principles to Manage Sediment:
• Reduce Sediment Production from the watershed
• If the sediment is produced, try to Hold sediment where it is
produced i.e. in the watershed itself
• If the sediment is produced, Manage it in the downstream without or
with less environmental damage

10. Reduce Sediment Production
• Foremost important principle of the sediment management is to reduce
the sediment production from the watershed.
• Reduce the soil erosion in the watershed by applying proper soil and
water conservation practice while using land and water
• How can we reduce Soil erosion from the watershed?-Key Issue
• Before we discuss, it is better we need to Refresh or Understand
what is soil erosion?

11. We define / understand Erosion as:
Process of detaching the soil particles by
erosive agents such as water, wind and gravity
from the land's surface of one place and it's
transportation to another place for deposition.
detaching
transportation deposition

12. Soil
1. Detach
2. Transport
3. Deposit
Rain Drop
Rain Fall

13. Soil Erosion Process consists of
Process at micro
level
Impact at macro /
landscape level
3) Deposition
2) Transportation
1) Detachment

14. How can we reduce sediment production from the
watershed?
• Any land use practices that reduce the soil detachment from its place
is the first step in reducing the soil erosion.
• More the soil disturbed, More will be the erosion.
• Tillage detach the soil from its
place, but without tillage we can
not grow crops.
• Conservation tillage or
minimum tillage operation in the
agriculture is one major
technique used in the agriculture
to reduce the soil detachment.

15. Contour Trenches – A Key Technique used in Afghanistan
How can we reduce sediment from Contour Trenches?
• Construction of contour trenches to hold the water in the watershed
does produce a lot of sediment because of significant soil disturbance
while constructing the trenches.
• Where contour trenches are
practices, most of the trenches
down below are filled with the
fine sediment produces from
trenches above.
• Also, the check dams
constructed in the gullies are
filled with sediment produced
from the trench digging.

16. Vegetation coverage plays important role in
reducing sediment
• The runoff study in Nepal
indicated that in the lack of
vegetation cover
• During pre-monsoon
(March to June), even
though rainfall is less than
30% of the annual rainfall,
• Annual soil loss
contributed 60% of the
annual soil loss

17. Promotion of Vegetation covering soil – Key Technique
to reduce sediment production

18. Techniques to promote the Greenery in the Dry Area
Contour Trench Water harvesting pond Spring
Runoff Water Harvesting
Mulching/PitcherMulching Pitcher Irrigation
Efficient Water Utilization Promoting Greenery

19. Hold sediment where it is produced!
• Growing crops, planting trees and carrying out any development, soil
need to be disturbed or dug, which helped first step of soil erosion.
• Soil disturbance is inevitable for our survival and development!
• Now the question is
• How the disturbed soil can be held in place, where it is disturbed.
• Second step of sediment management is holding the soil where it is
disturbed.

20. How could disturbed soil be held where it is produced?
• Providing protective coverage
• By providing vegetative coverage
• Structural coverage such as vegetative stone rip-rap
• Reducing carrying capacity i.e. transportation capacity of the eroding
agents.
• By Slope correction / Terracing
• Hedge row planting across the slope
Trapping Sediment
• Contour ploughing and planting and strip cropping are also agronomic
techniques of holding sediment where it is produced.
• Check dams construction

21. How can disturbed soil could be held in where it is produced?
• Water management by
• Increasing infiltration and Reducing runoff through water harvesting
in ponds
• Obstructing the flow through hedgerows / contour trenches
• These techniques help in holding sediment in the watershed.
Conservation Hedge rows Contour trenches

22. Management of sediment downstream
• No matter how much less soil is disturbed, and
• How much sediment is held in the watershed
• There will be some sediment coming down from the watershed in the
valley and plain.
• Key issue is
• How and where these sediments could be managed minimizing
downstream environmental degradation
• and
• Use these sediments for the betterment of the environment and
economic returns.

23. Trapping Sediment through Dam Construction
• Trap sediment and use as appropriate
• If the sediment is Good sand use
it for the construction.
• If the sediment is Good soil spread
it over agriculture field.
• Mostly Sediments is just good as
filling materials.
• Proper use of sediment could be an
economical incentive for
construction of sediment trapping
dam apart from reducing
environmental damage.

24. Spreading Sediment
• Irrigation system is built to distribute the water for growing crops and
vegetation.
• Designed the irrigation system to distribute the sediment uniformly
• Spreading flood water through construction of appropriate structures
• Spreading Flood Water also distributes the nutrients coming from the
watershed to maintain the fertility of the plain area.
• “Layers of silt deposited by rivers every year are essential for jute
cultivation in Bengal.
• Floods in the Nile too are also welcomed (by the people)
• In summary, what is needed is watershed management in the
Sedimentation Management

25. Watershed Management is Nothing But!
Putting the cap throughout the watershed area with Conservation Measures
(Mainly Vegetation)!!

26. Amu River:
Stream Bank Erosion and
Sedimentation
– Key Problems

27. • When Kulekhani watershed area observed more than 500 mm of rain in
24 hours (19-20 July 1993),
• 1 Ha. of watershed contributed 415 cu. m. sediment
• Numerous landslides and stream bank erosion are the main contributor
of the sediment.
Sediment Contribution

28. Stream Bank Erosion main source of sediment

29. Toe of the Slope!
Common techniques to support the falling
house!
Mark how a small wooden peg is
supporting poles and the pole holding
house!
If this peg is removed Whole House will collapse!

30. When slope
cutting
disturb the toe
of the slope it
triggers the
slope failure

31. Toe of the Slope
Toe protection of slopes can greatly reduce the
sedimentation downstream!

32. Nature’s Law: If slope angle is greater than the
Angle of Repose, slope fails!
Why slope once stable fails?What do you see?

33. Angle of Repose
Stable Angle maintained by Land Surface in Nature
(when heaped up on a platform)

34. Angle of Repose
• Angle of repose changes depending upon underlying Materials, Moisture
condition, and Conservation status
• With weathering: Underlying material changes
• With Rain: Moisture status change
• With Human Activities: Conservation Status changes
• So once the materials, moisture and conservation status change the slope has to
change to come to stable position again.
With rain moisture status changes, so the slope once stable failed as
moisture status changed with Rain.
What we have to do to reduce slope failure is understand Angle of
repose of the slope and Apply Conservation Measures accordingly!

35. Reducing Slope Failure
• Generally, underlying material could not be replaced to increase
stability!
• Controlling the rain to control moisture is not a pragmatic approach.
• However,
• Draining the moisture out of the slope through piping and
improving the drainage could be done effectively.
• Construction of diversion drainage to avoid moisture concentration
on the slope.
• Only way out is apply appropriate / pragmatic conservation techniques
to strengthen the angle of repose

36. • Different Technique are used to strengthen the angle of repose
• Mainly Through
• Providing vegetative coverage to the slope,
• Improving the infiltration capacity of the slope to reduce the
moisture content in the soil,
• Improving the soil binding capacity through root development.
• While designing conservation techniques to avoid the slope failure.
• It is important to understand the casual factor of the slope failure.
Conservation Techniques

37. Conservation Techniques
Title Description
Palisade Woody cuttings planted in line across the gully, usually
following the contour.
Fascine Bundles of live branches laid along the shallow gully.
Wattling Rows of fences made of vegetative materials (preferably live
cuttings) placed across the slope.
Brush layering A layer of woody cuttings planted in line across the slope,
usually following the contour.
Check dam A small, low dam constructed across a gully or any other water-
course.
Retaining wall A wall built to resist the pressure of earth filling or backing,
deposited behind it after it is built
Rip-rap Stone pitching for surface protection with mainly grass inter-
planted between the stones.
Palisade

38. Title Description
Conservation
plantation
Planting of vegetation especially grass, shrubs and trees species
along with necessary moisture conservation and protection
measures mainly on degraded lands including forests, barren
lands and gravelled and sandy river beds.
Conservation Techniques
Contour Buffer
Strip
Development
Planting of a permanent belt of erosion resistant vegetation
(trees, shrubs and grass) generally across the slope.
Water Harvesting
Conservation
Dam
Construction of dam for harvesting and storing runoff water.
Generally, dams are constructed across the rivulets or gullies or
valley to store the harvested runoff water.
Ground water
recharge
pit/trench
Construction of pits/trenches to recharge the groundwater
mainly through increasing infiltration by holding water in place.

39. Title Description
Irrigation
Channel
Improvement
Vegetative and structural measures applied to reduce erosion
damage to the existing irrigation channel caused by erosion
upslope or down slope or to reduce erosion damage caused by
the channel upslope or down slope lands.
Conservation Techniques
Terracing Refers to slope modification (levelling) of sloping agriculture
lands, management of drainage, and grass plantation on the
raisers to conserve soil and water.

40. Title Description
Landslide
Treatment
Vegetative and structural measures applied in the landslide area
and its influential catchment to stabilize the landslide.
Conservation Techniques
River/stream
bank protection
Vegetative and structural measures to protect the river/stream
bank and adjoining properties (habitation and farmland) from
erosion.

41. Title Description
Water and
sediment
management in
flood plain
Vegetative and structural activities applied to manage the water
and sediment coming to the flood plain so as to minimise
adverse impacts on the flood plain.
Conservation Techniques
Road slope
stabilization
Vegetative and structural measures applied in the road slope to
maintain stability of road and prevent erosion.

42. RIVER BASINS & CRYOSPHERE 42
Thank you