Vermelding onderdeel organisatie June 3, 2012 1 Environment Chapter 12 ct 4310 bed, bank and shoreline protection H.J. Verhagen Faculty of Civil Engineering and Geosciences Section Hydraulic Engineering
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Vermelding onderdeel organisatie
June 3, 2012
1
Environment Chapter 12
ct 4310 bed, bank and shoreline protection
H.J. Verhagen
Faculty of Civil Engineering and Geosciences Section Hydraulic Engineering
June 3, 2012 2
Introduction
• Ecologists stress that for a healthy environment there should be a good connection between land and water
• So shorelines are multifunctional elements in the landscape
• Main issues:
• use of vegetation
• allow animals to migrate from land to water and vice versa
• use of sustainable materials
• So:
• vertical walls are certainly not good
June 3, 2012 3
Other material
• Powerpoint presentation MilVriOev
• CUR manuals Natuurvriendelijke Oevers:
• 200 Aaanpak en toepassingen
• 201 Belasting en sterkte
• 202 Oeverbeschermingsmaterialen
• 203 Fauna
• 204 Vegetatie langs grote wateren
• 205 Water- en oeverplanten
June 3, 2012 4
ecological infrastructure
June 3, 2012 5
river as ecological connection with stepping stones
June 3, 2012 6
comparison
Space requirements versus
• discharge capacity,
• nautical possibilities, ect.
June 3, 2012 7
species and dynamics
June 3, 2012 8
food chain relations in a bank
June 3, 2012 9
hardly any exchange of life is possible between land and water
June 3, 2012 10
crossing location for mammals
June 3, 2012 11
planning and execution of steps
June 3, 2012 12
load and strength
June 3, 2012 13
Basic types of shoreline protection
June 3, 2012 14
filter tests for nature friendly fascine mattress
June 3, 2012 15
Reed and waves
June 3, 2012 16
Damping of wave loads
0.81 1 exp 0.001cos
TT
I
H BK N
H
N = number of stalks per m2
B = width of vegetation
= angle of incidence
0 for windwaves
55 for ship waves
June 3, 2012 17
wave damping and roughness in reed
June 3, 2012 18
roots as an armour against sliding
June 3, 2012 19
permissible flow duration on grass cover
June 3, 2012 20
reinforced vegetation
June 3, 2012 21
Vegetation growing through rock
June 3, 2012 22
Armorflex with vegetation
June 3, 2012 23
Roots in jute
June 3, 2012 24
Roots and Enkamat
June 3, 2012 25
exchange of water in strip due to passage of a ship
June 3, 2012 26
Berm along a shore
June 3, 2012 27
erosion between groynes
June 3, 2012 28
cross section of a coast with mangroves
June 3, 2012 29
wave transmission through mangroves (100 m)
June 3, 2012 30
Load reduction over a dam
0.31
1 exp( 0.5 )Tdam
I I
H BF
H H
B = crest width of the dam
Fdam: 0.64 rock
0.70 gabions
0.80 closed (asphalt, blocks)
June 3, 2012 31
wave transmission dams
June 3, 2012 32
water exchange possibilities
June 3, 2012 33
grass
• Grass is a flexible, renewable slope protection
• Grass can withstand quite some load
• Environmentalists do not like “monocultures”
• Fortunately from an engineering point of view, variation is also better
• Hydraulic engineers like roots, farmers like leaves
June 3, 2012 34
grass and clay layer
June 3, 2012 35
Texture formation in the clay body
Texture formation =
structuurvorming
Textured =
gestructureerd
June 3, 2012 36
“Maintenance”
Cattle and light fertilising
No cattle, removal of grass
Fertilising, and no removal of grass
Cattle, fertilizer and herbicides
June 3, 2012 37
load and strength of grass under wave attack
June 3, 2012 38
results of erosion tests
Fertilised +
cattle
Non-fertilised
after 25 yrs
Non-fertilised
June 3, 2012 39
erosion speed as function of wave height
June 3, 2012 40
Erosion speed of a grass turf
Quality cE
good 0.5 - 1.5
moderate 1.5 - 2.5
bad 2.5 - 3.5
max 2
E s
d dt
E c H
safety coefficient
E erosion speed
June 3, 2012 41
permissible duration of wave load and grass quality
June 3, 2012 42
Inner slope problems
Bosman, 2007
June 3, 2012 43
Inner slope erosion without cover
ComCoast, 2007
June 3, 2012 44
Reinforced grass
June 3, 2012 45
Conclusions
• Good grass cover does not show damage, even with very high overtopping discharges
• Grass with damages shows erosion with high overtopping rates
• Reinforced grass shows less damage in case of damage
• After removal of the grass cover, damage is considerable
June 3, 2012 46
Vetiver nursery
Agricultural University, Ho Chi Minh city, Vietnam
June 3, 2012 47
Vetiver as run-up reductor
June 3, 2012 48
Results of the experimental work
Algera, 2006 Vu, 2007
June 3, 2012 49
Bank protection with Vetiver
Jaspers Focks, 2006
June 3, 2012 50
Cumulative loss of bank materials Cumulative loss of bank material soil type C
0
1000
2000
3000
4000
5000
6000
7000
0 150 300 450 600 750 900 1050 1200 1350 1500 1650 1800
Number of cycles
Lo
ss
of
ma
teri
al (c
m^
3)
Soil C with Vetiver 1Soil C with Vetiver 2Soil C with Vetiver 3Soil C, fallow 1Soil C, fallow 2Soil MX with Vetiver 1Soil MX with Vetiver 2Soil MX with Vetiver 3
Jaspers Focks, 2006
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