Sinking coastal citiesA research agenda towards solutions for subsiding delta cities

Gilles Erkens – Deltares Research Institute | Utrecht UniversityTom Bucx – Deltares Research InstituteRien Dam - WaterLand Experts | Deltares Research InstituteGer de Lange – Deltares Research InstituteJohn Lambert – Deltares Research Institute

Land subsidence: why bother?

26 april 2014

Main messages:- Land subsidence outranges climate-driven sea level rise- Most of the problematic land subsidence is human-induced- Solutions are available and need to be found locally

26 april 2014

Main factors causing subsidence

Natural causes (geological processes):l Loading of the earth’s crust by ice sheets, sediment (delta’s),

the ocean/seal Compaction of older sediments after sedimentation

Anthropogenic causes (human-induced processes):l Oil/gas extraction (usually relatively deep)l Groundwater extraction (usually moderately deep)l Drainage of soils Þ oxidation of peat, soil compaction

Why discriminating between human-induced and naturalprocesses?l Magnitudel Cooping strategy (mitigation versus adaptation)

9 mlandsubsidencebetween1925-1977(52 years)~ 17.3 cm/y

Land subsidence vs absolute sea-level rise

26 april 2014

The sinking cities assessment

26 april 2014

1. How much subsidence is there?

2. What is causing subsidence?

A quick subsidence assessment for mega-cities:Jakarta, Ho-Chi-Minh City, Dhaka, New Orleans, Bangkok

3. How much subsidence is predicted?

4. What impact has subsidence?

5. Who is responsible?

6. What are solutions?

The assessment aims to:• Get insight in the

processes• To obtain a research

agenda for this topic• To list best practice

cases for others tolearn

NEW ORLEANS

JAKARTA

TOKYO

DHAKA

HCMC

BANGKOK

Impacts of land subsidence

26 april 2014

1) Flooding 2) Damage to structures

26 april 2014

What can we do?

Mitigation for human-induced land subsidence> Diminish pumping, aquifer storage recovery, use lighter building materials

Adaptation for natural and remaining human-induced land subsidence> reintroducing sediment in delta’s, build higher levees> Non-technical: better spatial planning, governmental embedding

26 april 2014

What can the geology community provide?

1. In-situ measurements2. Better subsurface models and maps3. Advising on solutions: geology-based spatial planning

Layers8. Aquifer 1

7. Aquitard 1

6. Aquifer 2

5. Aquitard 2

4. Aquifer 3

3. Aquitard 3

2. Aquifer 41. Aquitard 4

1

2

3

4

5

6

7

8

1 2

1-4

-59-69

-119-129

-169-179

-249

1-4

-59-69

-119-129

-169-179

-249

Level (m)