1. River morphology:
the science of sustainability
Erik Mosselman (extract of original presentation)
A joint meeting on river morphology, sediment transport,
catchment hydrology and flood forecasting issues
Himalaya Hotel, Lalitpur, Nepal, 15 March 2012
5. Fundamental concept: the Exner principle
∂zb dqs ∂u
+ =0
∂t du ∂x
erosion
sedimentation erosion sedimentation
top view side view
of flow in channel with uniform width
of flow over horizontal bed
11. Application: river narrowing for navigation
River bed degradation:
• Limited depth above fixed layers
• Restrictions for sluices and river
port entrances
• Instability of banks and hydraulic
structures
• Shift in discharge distribution at
bifurcations
• and for the Netherlands…
angry Germans!
12. Application: river narrowing for navigation
Johann Gottfried Tulla
In derrule, no
As a Regel,
keinriver or
Fluß oder
Bach derin the
stream Welt
brauchtneeds
world mehr
als ein Bett
more than one
bed
20. Application: river narrowing for navigation
Lesson learned:
River narrowing to improve navigability:
• effective on a short term
• leading to expensive measures to maintain navigability
on a long term
• due to river morphology
25. Application: water withdrawal for irrigation
sedimentation:
• rise in bed levels
• rise in water levels
water withdrawal
26. Application: water withdrawal for irrigation
sedimentation:
• rise in bed levels
• rise in water levels
• raised embankments
27. Application: water withdrawal for irrigation
sedimentation:
• rise in bed levels
• rise in water levels
• raised embankments
28. Application: water withdrawal for irrigation
sedimentation:
• rise in bed levels
• rise in water levels
• raised embankments
29. Application: water withdrawal for irrigation
sedimentation:
• rise in bed levels
• rise in water levels
• raised embankments
flooding
30. Application: water withdrawal for irrigation
Effect of water withdrawal
made worse in case of barrages and subsidence
flooding
31. Application: water withdrawal for irrigation
Lesson learned:
Water withdrawal for irrigation:
• lowers water levels on a short term
• raises flood water levels on a long term
• due to river morphology
33. There is more to river morphology …
RIVER MORPHOLOGY
Bed sediment
River shape composition
Bed Bed Bank Bank
degradation aggradation retreat advance