2. River Training Works
• Objectives
(i) To prevent the river from changing its course and to
avoid outflanking of structures like bridges, weirs,
aqueducts etc
(ii) To prevent flooding of the surrounding countries by
providing a safe passage for the flood waters without
overtopping the banks
(iii) To protect river banks by deflecting the river away
from the attacked banks
(iv) To ensure effective disposal of sediment load
(v) To provide minimum water depth required for
navigation
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3. Classification
• High water training or training for discharge: Flood
control- sufficient cross section for safe passage of
maximum flood and making adjoining area flood proof
by construction of dykes or levees
• Low water training or training for depth: Providing
sufficient water depth in navigable channels during low
water periods. Contracting and enhancing flow in
desired channel by closing other channels
• Mean water training or training for sediment: Efficient
disposal of suspended load and bed load. Most
important type as maximum accretion capacity of river
occurs in the vicinity of mean water or dominant
discharge
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4. Methods
• Marginal embankments or levees
• Guide banks
• Groynes or spurs
• Artificial cut-offs
• Pitching of banks and provision of launching aprons
• Pitched islands
• Miscellaneous methods such as sills, bandalling
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5. Marginal bunds/levees
• Earthen embankments
running parallel to river at
some suitable distance
from it
• Used for flood protection
by controlling the river
• Alignment follows
meandering of the river
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6. Guide Banks
• Build to train the river
for flowing axially
through a bridge.
• Provided in pairs in the
shape of bell mouth
symmetrical in plan and
either kept parallel or
may diverge slightly up-
stream of the works
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7. Spurs or Groynes
• Embankment type
structures constructed
transverse to the river flow
extending from bank into
the river
• Constructed to deflect the
current away from the
bank
• Nose of groyn is subjected
to tremendous action of
water and has to be
heavily protected
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8. • Constructed either singly or in series ( more effective)
• Groynes can be permeable or impermeable (solid)
• Permeable groynes do permit restricted flow through
them. Best suited for rivers carrying huge sediment
load in suspension
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10. Refer Garg 254-273
Write short note on Guide bunds, Groynes,
State the various types of river training works and explain the purpose
served by any two of them. [9]
What are merits and demerits of river training by levees? Describe how
a river is controlled with the help of levees? [8]
What is cut off? Describe briefly how a cut off may be used as river
training measure?
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11. Cutoff
• Development of chord or straight
channel by abandoning the meandering
channel
• Natural phenomenon for
counterbalancing the ever increasing
length of river
• During high floods more and more tend
to flow through side channel
• Reduced flow in main channel increases
silting in main channel and further
increase in flow in side channel
• A time comes when entire flow flows
through chord channel
• A cutoff can be induced artificially if
meandering course endangers some
valuable land or property
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