Centre for Flood Control and Water Management inWestern Province, Sri Lanka
GEOSS Asia-Pacific Symposium, 11-13 January 2017, Tokyo, Japan

Srikantha Herath
Senior Advisor, Ministry of Megapolis and Western Development, Sri Lanka
Visiting Professor: UNU, Institute for the Advanced Study of Sustainability, Japan
Visiting Professor: The University of Tokyo, Japan
Visiting Professor: University of Peradeniya, Sri Lanka

January 12, 2017

Srikantha Herath (Megapolis)

GEOSS/IFI

January 12, 2017

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Metro Colombo Drainage System
City protected by bunds andgates from Kelani River floodwaters. However, overflow ofcanals at extreme local rainfall
events cause severe flooding.
Colombo is extremely flat andthe very small slope makes
drainage extremely difficult.
Currently drained by 3 sea
outfalls and two Kelani riveroutfalls.
Lakes and marshy lands provides
considerable storage formanaging floods.
Srikantha Herath (Megapolis)

GEOSS/IFI

January 12, 20172 / 11

Addressing Floor Risk
Present Status

After Intervention

Metro Colombo Urban Drainage Project with a World Bank Loan is
improving city drainage capaicty
Canal Improvments, two tunnels and 3 pumping stations wouldincrease outfall volume.
Srikantha Herath (Megapolis)

GEOSS/IFI

January 12, 20173 / 11

Managing Future Risks
New Development Programme: Megapolis Development
Need to assess increasing flood vulnerability and design counter measures.
THE MEGAPOLIS
Western Region Master Plan
“From Island to Continent ”

Increase green
infrastructure: Surface
retention (wetlands) andInfiltraiton

I

Risk assessment onmajor developments,
Transport Hub, Port
City, etc.
Real Time Monitoring
and Control

Srikantha Herath (Megapolis)

100

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Srikantha Herath (Megapolis)

GEOSS/IFIJanuary 12, 2017

5 / 11Retention and reusepany Profile I> Totetsu’s Technology

u is a NeedJapanesemanufacturingcompany, which has a series ofto increase
flood control
ology that can turn rainwater into a major water source.

capacity considering futureCollecting
and initialdevelopment
purifying technology

UndergroundSystem
<Company ProfileI>Water
Totetsu’s
Technologyompany
ProfileI> Totetsu’s
Difficultyof drainage:
Low Technology
gradient

Totetsu is a Japanese manufacturing company, which haotetsu is a Japanese manufacturing company, which has a series ofDifficulty intechnology
major constructions
that can turn rainwater into a major water source.
chnology that can turn rainwater into a major water source.

in congested capital

Collecting and initial

Collecting and initial

Underground
Water SystemUnderground Water Sys
purifying technology
FromStormWater Drainage
to WaterCycle Management
purifyingtechnology

ark Source:
ProjectAssociation for Rainwater Storage and Infiltration Technology (ARSIT)

bove-ground water tank

Srikantha Herath (Megapolis)

GEOSS/IFI

January 12, 20176 / 11

9%

URM
41%

URM

Risk Assessment: Potential Loss and Response
Loss Functions

Figure 3.7: Surveyed building types and their percentageResidential
distributionsUnreinforced Masonry (URM) Residential Concrete Frame with URM
WoodenAB

Der
Commercial

Adopting Standard
Building Categories:
Wood, All Steel
Structures, All Concrete
C
Frames(3), All
Masonry(2), Adobe, Slab43%

Unreinf
Masonry(URM)

ConcretwithLo
Residential Unreinforced Masonry (URM) unreinfo
ResideMasonryB
Walls
Commercial BuildingFigure 3.7: Surveyed building types and their percentage distributions

AResidential Wooden Structure

WoodenCommebuilding

Critical Infrastructure
MappedFigure 3.8: Examples of residential building types found in the field: A. URM, B. CFURM, C. Wooden

Comprehensive Exposure
map being prepared for
Economic Risk
Assessment and Risk
based warning.
Srikantha Herath (Megapolis)

Building

Residential Wooden Structure

C73MaxWooUnre
Conc
19%
Com

19

Figure 3.8: Examples of residential building types found in the field: A. URM, B. CFURM, C.

GEOSS/IFI

January 12, 20177 / 11Inter Agency Collaboration: Trigger: May 2016 Floods

Colombo Page 17th May

Colombo Telegraph 19th May

11 major floods in last 32 years.
Biggest since 1989. (SW monsoon
from May to September)
Heavy rains in mid, upper and lower
Kelani basin from 13th to 19th :catchment average 515 mm total.
280,444 people affected, 96 deaths,4877 displaced.
722 houses completely destroyed.
Over 5000 partially damaged.
Srikantha Herath (Megapolis)

GEOSS/IFI

APPhoto 20th May

Discussions among major
stakeholders in 2016 Aug - Oct
Form an inter-agency platform for
integrated information system
A Steering committee senior
management and a working groupnominees from the stakeholder
organizations formed.
Cabinet approved the establishmentof a state-of-the-art-center.
January 12, 20178 / 11CFCWM – RTC Implementation

Srikantha Herath (Megapolis)

GEOSS/IFI

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Summary: Metro Colombo Urban Flood Control

Improving basic drainage infrastructure to cater to 1:50 yr rainfall,
favourable boundary conditions, through canal improvements, tunnels
and pumping stations
Assessing Future Risk From Development, On Development(infrastructure)
Detailed mapping for risk based warning (people, assets)
Moving from quick storm water discharge to storing water in lakes,
wet lands and underground
Real Time Forecasting and Control with inter-agency collaborationSrikantha Herath (Megapolis)

GEOSS/IFI

January 12, 201710 / 11

Thank You!

Srikantha Herath (Megapolis)

GEOSS/IFI

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