The future of deltas in the
perspective of environmental
change
Harmonizing human interests and
environmental interest is one of the
largest challenges for human
mankind
6th Lustrum of theWaterbouwdispuut
The future of deltas
• Ho Chi Minh City and its estuarine and tidal
river delta (a typical example of a growth
economy in SE Asia)
• The Southwestern Dutch delta (a typical
example of an established protected delta
seeking for harmony with nature)
Phuoc Hoa dam
Be
Dau Tieng dam
Tri An dam
Thu Dau Mot
Sai Gon
Dong Nai
The problems
of HCM City
Ho Chi
Minh
City
Vam
Co
Dong
Nha Be
Hiep
Phuoc
Dong Thap Muoi
Long
Tau
Cai Mep/
Thi Vai
Soai
Rap
Vam Co Tay
Can
Gio
Vam Co
Can Thanh
Go Cong
East Sea
Vung Tau
March 29 2011
Hanoi
Main stakeholders
City
Agriculture
Shipping
Nature
Phuoc Hoa dam
Be
Dau Tieng dam
Tri An dam
Thu Dau Mot
Sai Gon
Dam
Vung Tau – Go Cong:
the IJssellake
solution
Dong Nai
Ho Chi
Minh
City
Vam
Co
Dong
Nha Be
Hiep
Phuoc
Dong Thap Muoi
Long
Tau
Cai Mep/
Thi Vai
Soai
Rap
Vam Co Tay
Can
Gio
Vam Co
Can Thanh
Go Cong
East Sea
Vung Tau
March 29 2011
Hanoi
Idea: “valve” lowers water levels ......
Simplified
approach
River flow
Basi
n
Tide
1.50
Dam with
valve
No dam,
original
situation
1.00
30.000 m3/s
river flow,
valve 10.000
m2
Waterlevel
0.50
0.00
-0.50
-1.00
-1.50
-2.00
-2.50
Time
5.000 m3/s
river flow,
valve 10.000
m2
...... and keeps
salt water
outside
Result depends on:
• River flow
• Valve size
• Basin size
River flow 30.000 m3/s
2
Max water level in basin
1.8
1.6
Basin 200
km2
1.4
1.2
1
No dam, original
situation
0.8
0.6
0.4
Basin 300
km2
0.2
0
0
10000
20000
30000
Valve size
40000
50000
60000
Real situation more complex:
1.5
1
0.5
Effect
over
whole
period
0
-0.5
-1
Effect
-1.5
during
springtide
No dam
With valve
Shipping
Maximum permissible velocity ~ 4 knots = 2
m/s
Necessary width ~ 200 – 300 m
But: valve closed during flood → locks
Phuoc Hoa dam
Be
Dau Tieng dam
Possible alternative 1
combination of
IJssellake and
Haringvliet solution
Tri An dam
Thu Dau Mot
Sai Gon
Dong Nai
Idea:
• Lowering level HCMC
• Lowering salinity Dong Thap Muoi
• Maintaining tide and salt Can Gio
• Maintaining shipping route Cai
Mep
Ho Chi
Minh
City
Vam
Co
Dong
Nha Be
Hiep
Phuoc
Dong Thap Muoi
Long
Tau
Cai Mep/
Thi Vai
Soai
Rap
Vam Co Tay
Can
Gio
Vam Co
Can Thanh
Go Cong
East Sea
Vung Tau
Phuoc Hoa dam
Be
Dau Tieng dam
Possible
alternative 2
Tri An dam
Thu Dau Mot
Sai Gon
Dong Nai
Idea:
• Lowering level HCMC
• Lowering salinity Dong Thap
Muoi
• Maintaining tide and salt Can
Gio
Cai Mep/
Thi •
VaiMaintaining shipping route Cai
Mep
Ho Chi
Minh
City
Vam
Co
Dong
Nha Be
Hiep
Phuoc
Dong Thap Muoi
Long
Tau
Soai
Rap
Vam Co Tay
Can
Gio
Vam Co
Can Thanh
Go Cong
East Sea
Vung Tau
Provisional conclusions
•
Idea promising for lowering water levels with
moderate river flows
• For extreme river flow, it will be difficult
• For detailed studies consistent data needed (salt,
velocities, discharges, ….)
• Take other issues into account, e.g. subsidence
Dutch experience:
soil subsidence
more important
than sea level rise
The Dutch Southwestern Delta
Perceived
problems
The Dutch Southwestern Delta
Perceived
problem: no
salt-fresh
water gradient
The Dutch Southwestern Delta
Perceived problem:
Stagnation due to
absence of
fresh/salt water
gradient
The Dutch Southwestern Delta
Perceived problem:
Starving intertidal
areas
The Dutch Southwestern Delta
Perceived problem:
Restoration of
intertidal, lowdynamic regions
The Dutch Southwestern Delta
Solution: restore
intertidal areas by
depoldering but
polictically
unacceptable
The Dutch Southwestern Delta
Political solution:
restore intertidal
areas by creating
these areas in the
current outerdike
space!
Nonsense!
Conclusions
• Growth economies are facing a challenging
time: how to combine economic growth with
environmental concerns
• Established economies are facing a challenge
as well: how to restore environmental values
against economic interests