The future of deltas in the perspective of environmental
changeHarmonizing 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)
Sai Gon
Long Tau
Vam Co
Vam Co Tay
Vam Co
Dong
Dong Nai
Soai Rap
Can Gio
Vung Tau
Ho Chi Minh City
Nha Be
Go Cong
East Sea
Be
Can Thanh
Hiep Phuoc
Dau Tieng damPhuoc Hoa dam
Tri An dam
Cai Mep/ Thi Vai
Dong Thap Muoi
Thu Dau Mot
The problems of HCM City
March 29 2011Hanoi
Main stakeholders
Shipping
NatureAgriculture
City
Sai Gon
Long Tau
Vam Co
Vam Co Tay
Vam Co
Dong
Dong Nai
Soai Rap
Can Gio
Vung Tau
Ho Chi Minh City
Nha Be
Go Cong
East Sea
Be
Can Thanh
Hiep Phuoc
Dau Tieng damPhuoc Hoa dam
Tri An dam
Cai Mep/ Thi Vai
Dong Thap Muoi
Thu Dau MotDam
Vung Tau – Go Cong: the IJssellake
solution
March 29 2011Hanoi
Idea: “valve” lowers water levels ......
River flow
Tide
5.000 m3/s river flow,
valve 10.000 m2
30.000 m3/s river flow,
valve 10.000 m2
Basin
Dam with valve
No dam, original situation
...... and keeps salt water
outside
Simplified approach
Result depends on: • River flow• Valve size• Basin size
No dam, original situation
Basin 200 km2
Basin 300 km2
River flow 30.000 m3/s
Real situation more complex:
Effect over
whole period
Effect during
springtideNo dam
With valve
ShippingMaximum permissible velocity ~ 4 knots = 2
m/s
Necessary width ~ 200 – 300 m
But: valve closed during flood → locks
Sai Gon
Long Tau
Vam Co
Vam Co Tay
Vam Co
Dong
Dong Nai
Soai Rap
Can Gio
Vung Tau
Ho Chi Minh City
Nha Be
Go Cong
East Sea
Be
Can Thanh
Hiep Phuoc
Dau Tieng damPhuoc Hoa dam
Tri An dam
Cai Mep/ Thi Vai
Dong Thap Muoi
Thu Dau Mot
Possible alternative 1combination of IJssellake and
Haringvliet solution
Idea:• Lowering level HCMC
• Lowering salinity Dong Thap Muoi• Maintaining tide and salt Can Gio• Maintaining shipping route Cai
Mep
Sai Gon
Long Tau
Vam Co
Vam Co Tay
Vam Co
Dong
Dong Nai
Soai Rap
Can Gio
Vung Tau
Ho Chi Minh City
Nha Be
Go Cong
East Sea
Be
Can Thanh
Hiep Phuoc
Dau Tieng damPhuoc Hoa dam
Tri An dam
Cai Mep/ Thi Vai
Dong Thap Muoi
Thu Dau Mot
Possible alternative 2
Idea:• Lowering level HCMC
• Lowering salinity Dong Thap Muoi
• Maintaining tide and salt Can Gio
• Maintaining shipping route Cai Mep
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, low-
dynamic 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