UGEC20102010/10/17 at Arizona State University

Field-level adaptation to floods and sea level rise in coastal peri-urban areas in monsoon Asia:

Comparative case studies betweencontinental Bangkok and insular Metro Manila

Yuji Hara1 & Danai Thaitakoo2

1: Wakayama University, Japan2: Chulalongkorn University, Thailandhara@sys.wakayama-u.ac.jp

UGEC2010Asian large cities (population > 5million);Located on continental delta / insular lowlands

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UGEC2010Purpose of this presentation

To show present case studies on landform transformation (LT) in response to flooding in continental Bangkok and insular Metro Manila

– Horizontal land-use changes– LT processes– LT and floods– Field-level responses to floods (by local people

and government)– Toward land-use and LT integrated planning for

minimizing a flood hazard

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UGEC2010

0 100km

Built-up area

Continental Bangkok

Built-up area

0 100km

Insular Metro Manila

Case study cities

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UGEC2010

UGEC2010

(Hara et al. 2005)

Horizontal land-use change:From rice fields to townhouses

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UGEC2010Vertical LT process:From dig & fill to introduced fill

Clay fill (CL, 5Y5/1)

Water body

Sand fill (S, 10YR6/6)

Crushed rock

Concrete plank

Material (texture, color)

OrchardKhlong houses

1987 Land use

2000 Land use

5m

0

-5m

Soil pitFishpondInstitutionKhlong houses

Orchard

WastelandWastelandRice field

Ricefield

InstitutionApartmentsKhlong houses

Khlong houses

Orchard

1000m1500m

Khlong

Road

Rice fieldFishpond

Townhouse

Rice fieldFishpond

Vacant land

Townhouse

Rice field

TownhouseTownhouse

(Hara et al. 2008a)0

50,000

100,000

150,000

200,000

250,000

300,000

1952 1967 1979 1987 1995 2002

Volu

me

(m3 /

km2 )

Year

7

UGEC2010Introduced fill from further areas (the rim of delta)

Fill volume (Hara et al. 2008a)Production: 5.5×107 m3 year−1

Input: 5.7×103 m3 km−2 year−18

UGEC2010Flood characteristics:Sheet flow and parcel-level water management

Floods come gradually Water level is manageable

per each parcel using private pump with gasoline engine

0

0.5

1

1.5

2

2006/4/1 2006/5/1 2006/6/1 2006/7/1 2006/8/1 2006/9/1 2006/10/1 2006/11/1 2006/12/1 2007/1/1 2007/2/1 2007/3/1 2007/4/1

Water level of main stream of Chao Phraya River (at Nonthaburi monitoring sta.)

(using RID data)

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UGEC2010Temporal adaptation to sheet flow flooding

Using sandbags to build temporal banks to protect water coming in, and then releasing floodwater to the canal by pumping

Using a boat, that was traditionally utilized as a main transportation mode and still kept along the canal

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UGEC201010 – 20 years adaptation to rising water baseline due to the loss of flood retention capacity by introduced fill

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Lifting up a pathway and a road

Lifting up a floor(as their traditional house structure)

UGEC2010Suggestions for spatial planning

Main problem on the current planning process– No linkage between land-use plan and water

management plan

Toward better planning– Zoning based on acceptable fill (water) volume

that can induce field-level adaptation using inherent LT methods

– Focusing not only on regulative measures but more on incentive ones (for instance bonus floor area ratio for preparing ponds)

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UGEC2010

0 100km

Built-up area

Continental Bangkok

Built-up area

0 100km

Insular Metro Manila

13

UGEC2010Coastal Plain – Central Upland – Eastern Plain

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UGEC2010Horizontal land-use change:From natural micro landform basis to LT basis

(Hara et al. 2008b) 15

UGEC2010Vertical LT process: Landfilling on lower landforms

1986 Land use

2004 Land use

5m

0

-5m

500m

Rice field

Swamp

Vegetable patch

Vegetable patch

Detached houses

Detached houses

P.Rosales Street

Slum-type housing

Slum-type housing

Slum-type housing Detached houses

Detached houses

1966 Land useRice fieldDetached houses

Forest Detached houses

Clay fill (HC, 2.5Y3/3)

Water body

Sand fill (S, 5Y5/1)

Crushed rock

Construction waste (broken concrete etc.)

Material (texture, color)

(Hara et al. 2008b)

0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

400,000

1966 1986 2004

Year

Vol

ume

(m3 /k

m2 )

Lacustrine delta &Lacustrine plainLower lacustrine terrace

Upper lacustrine terrace

Natural levee

Back marsh & Valley plain

Upland

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UGEC2010Flood characteristics: Flash flowEastern plain as “flood control pond” to protect downstream central Manila

(Hara et al. 2002)17

UGEC201010 – 20 years adaptation: Individual landfilling up to the highest flood level in their experiences

Adapting themselves to their own experiences without any consideration of neighbors and flood control scheme by the government 18

UGEC2010It has caused changes in distribution of flood-prone areas and required temporal adaptation

SPOT 1987/11/18 SPOT 1997/10/26

(Hara et al. 2002)

Emerging submerged areas with poor drainage surrounded by landfill corridor

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UGEC2010New threat due to infrastructural development

Tropical Storm Ondoy

Flooded Areas

(NAMRIA 2009)

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UGEC2010New infrastructures accelerated flash flow hazard

ALOS PALSAR image soon after Ondoy(Modified after NAMRIA 2009)

Newly built bridges trapped a lot of debris, and functioned as temporal dam during Ondoy

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UGEC2010Failure of planning: Subdivision out of lakeshore dike

It was built before the construction of lakeshore dike in 2004

(not subject to zoning code?)

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UGEC2010Suggestions for spatial planning

Main problem on the current planning process– Land-use plan is based only on road network

Toward better planning– Landfill practice should be subject to micro

landform to avoid poor drainage area surrounded by landfill corridor

– Need to coordinate landfill material flows between suppliers and consumers

– Link between infrastructures (including non flood protection ones) and land uses

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UGEC2010Summary matrixBangkok Metro Manila

Landform • Continental delta• Homogeneous flat plain

• Insular lowlands• Visible micro landforms

Floods • Sheet flow• Water level is manageable

per each parcel using pumping

• Flash flow• Water level is

unmanageable without public infrastructures

LT methods • Dig and fill development• Fill from further area

• Landfilling using construction debris

Field-level adaptation

• Temporal banks• Changing transportation• Lifting up pathway & floor

• Individual fill on the floor• Evacuation boat• Staying upper floors

Similar case studies are being carried out in other Asian low-lying cities… 24