flood management strategiesmarketing.geo.com.tw/2018ifwc/download/11081101_keynote04.pdf · flood...

Flood Management Strategies in Taiwan -- Extreme Rainfall

Dr. Chien-Hsin Lai Director-General Water Resources Agency (WRA), Ministry of Economic Affairs (MOEA)

1

Flood Management Strategies in Taiwan

Where we live

What we think

How we do

Conclusions

1

2

3

4

2

Where we live Chapter. 1

4

Geographic location of Taiwan

China

Taiwan

Japan

Russia

Mongolia

South Korea

North Korea

Philippines

Malaysia

Indonesia

Vietnam Thailand

Laos

Myanmar

Chapter 1. Where we live 5

Country Date Casualty

Taiwan 0823 7 deaths, 8492 evacuations

Philippine 0812 54,000 evacuations

Myanmar 0731 11 deaths, 120,000 evacuations

Laos 0723 Dam Break 27 deaths, 1126 missing

Japan 0705 105 deaths, 87 missing

Vietnam 0625 7 deaths, 12 missing

China 0507 6925 evacuations

Malaysia 0104 9000 evacuations

FLOOD

Asian events occurred in 2018

Penghu (1974)

1 hr 1 day 2 day 3 day

Kauai USA

(1956)

Pingdung (2009)

Réunion France (1966)

Pingdung (2009)

Cherrapunji India

(1995)

Pingdung (2009)

Réunion France (2007)

Taiwan record (mm)

World record (mm) up to 2009


The extreme events

are equivalent to the world records

Storm event rainfall

(mm/hr)

2016/ Nesat 181 2017/ 06.01 132 2018/ 08.23 121

Source: Taiwan WRA, 2017


Short concentration time

Source: River planning report.

River Concentration

time (hr)

Danshuie 15.4

Jhuoshuei 18.35

Zengwun 15.44

Yanshuei 14.55

Gaoping 14.45

Lanyang 7.13

Hualien 7.24

Mekong 458

Rhine 342

Colorado 94 Distance (km)

Rhine River (Europe)

Comparison of River Slope

Elevation (m

) Colorado River

(USA)

Taiwan’s Rivers

Japan’s River

Estuary

Mekong River (Asia)

8

No typhoon

1 typhoon

2 typhoons

3 typhoons

4 typhoons

5 typhoons

6 typhoons

7 typhoons

Picture: Lin; source: CWB

Definition of attack: 1. Typhoon center

landing 2. With no center

landing, but cause disaster on land

Number of typhoon attacks during 1911-2017

Chapter 1. Where we live

Threats by typhoons Average: 3.5 typhoons / year

Typhoon Cimaron

Typhoon Trami

Typhoon Usagi

Typhoon Fitow

Typhoon paths in 2013


Hazards induced by extreme events

Area Event Total rainfall

(mm)

Increased

area of

landslide (Ha)

Reduced volume

percentage (%)

Shihmen Reservoir 2004Typhoon Aere 1,022 326 12.2

Zengwun Reservoir 2009Typhoon Morakot 3,058 1,126 9.0 ? ?

Line/Scatter Plot 3Line/Scatter Plot 1曾文水庫石門水庫

賀伯颱風後

921

大地震後

桃芝颱風後

艾利颱風後

海棠颱風後

六九豪雨後

柯羅莎颱風後

卡玫基颱風後

莫拉克颱風後

凡那比颱風後

南瑪都颱風後

蘇拉颱風後

蘇力颱風後

麥德姆颱風後

蘇迪勒颱風後

尼伯特颱風後

尼莎颱風後

921

大地震前

艾利颱風前

娜克莉颱風後

Increased area of landslide 1126 ha Increased area of

landslide 326 ha

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

La

nd

slid

e a

rea

(h

a)

Afte

r Typ

ho

on

He

rb

Be

fore

92

1 e

arth

qu

ak

e

Afte

r 92

1 e

arth

qu

ak

e

Afte

r Typ

ho

on

Tora

ji

Afte

r Typ

ho

on

Na

kri

Afte

r Typ

ho

on

Ae

re

Be

fore

Typ

ho

on

Ae

re

Afte

r Typ

ho

on

Ha

itan

g

Afte

r Jun

e sto

rm

Afte

r Typ

ho

on

Kro

sa

Afte

r Ty

ph

oo

n K

alm

ae

gi

Afte

r Ty

ph

oo

n M

ora

ko

t

Afte

r Ty

ph

oo

n F

an

ap

i

Afte

r Ty

ph

oo

n N

an

ma

do

l

Afte

r Typ

ho

on

Sa

ola

Afte

r Typ

ho

on

So

ulik

Afte

r Typ

ho

on

Ma

tmo

Afte

r Ty

ph

oo

n S

ou

de

lor

Afte

r Ty

ph

oo

n N

ep

arta

k

Afte

r Typ

ho

on

Ne

sat

Shihmen Reservoir

Zengwun Reservoir


Threaten by compound disasters

71.5%

8.4% 38.0%

1.4%

8.5%

21.5%

1.4%

Highly Flooding prone area

Highly Debris Flow

prone area

Highly Landslide prone area

What we think Chapter. 2

Chapter 2. What we think 12

Highly concentrated population in the cities

Northern and urban population has a growing trend

Population growth rate (%) in 6 major cities

(2009.10-2018.10)

City Urban Rural Total

Taipei 2.4 2.4

New Taipei 5.2 -15.3 3.3

Taoyuan 30.4 -28.4 12.2

Taichung 8.0 1.0 6.3

Tainan 2.3 -8.5 0.5

Kaohsiung 2.5 -13.3 0.1

Population growth rate (%)

Source: Statistical Yearbook of Interior- Department of statistic, Ministry of Interior (2018)

City Urban area(Ha) River area (Ha) (%)

Taipei 27,180 1,794 6.6


Urbanization reduces river space

Source: Westerner in Taiwan (KP17)


Near future

Near future

Near future

Near future

Mid of century

Mid of century

Mid of century

Mid of century

End of century

End of century

End of century

End of century

north central

south east

Va

ria

tio

n (

%)

Va

ria

tio

n (

%)

Va

ria

tio

n (

%)

Va

ria

tio

n (

%)

Variation of storm days

Under the RCP 8.5 scenario, the days of extremely heavy rain would increase over 70% in the end of 21 century. The highest variation is in central area (+128%).

Taiwan is threaten by climate change


Rain

fall s

cale

Only protect for the usual events (high occurrence probability) •Protection standard for farm drainage

– 10 years recurrence interval，1-day average drainage

•Protection standard for rainfall sewer – 2~5 year recurrence interval

•Design standard for regional drainage – 10 year recurrence interval

•Protection standard for slopeland farm drainage – 10 year recurrence interval

• Build the detention facility • Building management and disaster prevention • Green infrastructure • National spatial planning and reallocation • Flood insurance

Resilient community, resilient city • Mitigate the disaster level in the system; • Reduce the recovery time of the system; • Enhance the learning capacity during the disaster

Gra

y e

ng

ineerin

g

Gre

en

en

gin

eerin

g

Extreme event Flooding

unavoidable

Normal

event

Pro

tectio

n b

y

stru

ctu

re

Pro

tectio

n b

y

no

n-s

tructu

ral

Resilient City

Source :Pao-Shan Yu, Briefing on the flooding symposium in the Mino district of Kaohsiung City(Aug 12, 2018)

How we do Chapter. 3

Strategy

17 Chapter 3. How we do

A


Topping on the cake (Land) Parks and sidewalks were piled up in the cities; roads are the

lowest place in the city

Flooding in the roads brings inconvenience to the residents.

0702 event in 2018 (Yuanlin City)


Road effects Problem of water blocked by roads

Guo-Gou Village


Road effects Embankment effect

Village protection facilities

Elevated road

Wang-liao Villiage


Utilize road design flexibly Improve collection efficiency of the inlets Improve the side-ditch size and spacing of connection pipe Apply LID facility for the sidewalk Take the embankment effect as evaluation focus in the outflow regulation

project. Check whether the discharge capacity or drainage basin is affected.

Permeable pavement Rain detention


Integrate road and drainage system

Use traffic system to deliver flood- road discharge

Excavate divisional island- green street Detention facility in the node of road system-

interchange detention pond

Reduce the elevation of divisional island to increase water storage

Provincial Highway 61 Shalu Interchange

Set the detention pond in system interchange

Denver road discharge

Strategy


B

Chapter 3. How we do 24

An Extreme Precipitation will exceed the capacity of rainwater sewer systems and cause flooding.

Runoff Distribution


Runoff Distribution

River

Parking

lot

Green

land

School

Park

The runoff can be distributed over the public spaces, such as rivers, parks, parking lots, schools, and green spaces.


Runoff distribution and outflow regulation

Share the water both in the waterway and land. The amendment of the Water Act was promulgated on June 20, 2018.

Outflow regulation

Resilience

Government

Applied in the site area

Development sector

Response to the runoff

increase by climate change

Response to the runoff

increase by development

Development case beyond

specific scale

Runoff Distribution

Specific watersheds &

basins by declaration

Prior to public land

New constructed public

facility with detention

function，ex: park, road

drainage, etc.

Apply the detention pond,

low impact practice, etc.

on site to reduce runoff

purpose

obligor

range

method

practice

27

“Maple Garden” in Taichung City has functions of flood detention, drainage and recreation.

Constructed in 2012; total storage capacity is 200,000 m3.

Maple Garden

Source：Taichung City Government

28

“Benhe Detention Park” in Kaohsiung City applied the ecological engineering to have the functions of landscape, detention and recreation.

Constructed in 2008; total storage capacity is 100,000 m3.

Benhe Detention Park

Source：Kaohsiung City Government


Outflow Regulation

29

pre-development post-development post-development +

flood mitigation facility

outflow outflow outflow

Urbanization increases flood risk

The land developers construct the detention basins and Low Impact Development facilities.

Completed in 2014 Total storage capacity of 8,000 M3 Reduce flood risk of surrounding 10 ha,

and protect 1700 residences

Donghu Detention Basin

In Dali Software Park


Completed in 2015 Total storage capacity of 32,000 M3 A multi-purpose park with ecological,

landscape, flood detention and recreation.

Flood detention Basin in

Pinglin Forest Park


Strategy


C Detention on site


Land use fits in spatial planning

Agriculture

67.7%

Others

Traffic

Hydrological

4.5%

Building

Forest

Land use Area(Km2) (%) Agriculture 874 67.7

Forest 104 8.0 Traffic 80 6.2

Hydrological 58 4.5 Building 103 8.0 Others 73 5.6 Total 1292 100

*land use distribution in Yunlin County *Source: department of land administration, MOI

Levee

Levee

Village


Case study in Loisach River, Germany

Flood area

Levee is constructed to protect village. Farm lands share flooding water. No destroy of the original usage. Allows flood entering the farms during the storms. Combination of levee and grass land; the landowner could get one time

compensation of 20% of current value.

Source :Bavarian State Water Authority, 2010 Bavarian Rural Development and Water Management Mission


Detention on site

Apply the idle/ fallow farm and fishing pond to share the flood storage during storms.

Modified

Wa-Yao Village Flood simulation of 100-year return period

Flooded area 4.6 ha, flooding depth 0.4 m in village No flooding in village Farmland 80 ha

Strategy


D


Early warning Rainfall in Gangshan station on Sep. 19 in 2010 (Typhoon Fanapi )

0

100

200

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

雨量(

毫米)

Flooding at 15:00 at the nursing home

Rescue team arrive at 20:00

Flood prediction get 3hr earlier for

response

24 1 2 3 4 5 6

Ra

infa

ll (

mm

)

3Hours

Before: wait for rescue Now: evacuation beforehand

Get 8 hrs for response


Improve the rainfall radar system

Provide the higher resolution of rainfall spatial distribution

Before resolution：1.3Km x 1.3Km

After resolution：250m x 250m

The maximum rainfall observed by Linyuan radar 23mm/hr

The maximum rainfall observed by the old radar 22mm/hr


Spatial and temporal distribution of rainfall along Xinyi Road (from east to west)

0908 storm event

Daan Forest Park MRT Dongmen station Sec. 1, Xinsheng S. Rd.

Flooding from east to west

Application of radar data for precipitation monitoring


Real-time Flooding Forecasting System

Automatically input the next 3 hr predicted rainfall to the 2-D model to forecast the flooding in next 3 hr with the resolution of 40*40 m.

Typhoon Megi in 2016

INPUT

Future precipitation forecast by CWB


Flood prediction online system Automatic, real-time and dynamic

Flood warning, flood

depth, flood duration Results exhibition

Big data database

AI

Big data

Machine

learning

Exhibition

Apply the simulation results of the flood models to cut down the calculation duration from 30 mins to seconds and train the AI and machine learning.

Guoxing Bridge

Xigang Bridge

Mashan Bridge Danei

Bridge Erxi Bridge

大內八號橋

大內十號橋

玉豐大橋

中正橋

曾文一橋

曾文二橋

Taitie Bridge

Not satisfied to project flood

Close to waterway or scour directly

High liquefaction potential layer

Basis depth is not sufficient

Section 1 Section 2 Section 3 Section 4 Section 5 Section 6

Liaobu levee (high risk) dam failure simulation


Risk assessment for watershed

Risk analysis provides well information to prevent and mitigate disasters


Smart Water Level Gauge

Smart water level gauges are set up to detect the inundation depths on the roads and to assess the accuracy of model.

The research results indicated the accuracy of the flood forecasting system has reached 88.9%.

0

0.2

0.4

0.6

9 12 15 18 21 0 3 6 9

Inu

nd

ati

on

de

pth

(m

)

Time (h)

Station D in Typhoon Megi

SimulationObservation

0

0.1

0.2

0.3

9 12 15 18 21 0 3 6 9

Inu

nd

ati

on

de

pth

(m

)

Time (h)

Station I in Typhoon Megi


0

0.1

0.2

0.3

0.4

0.5

9 12 15 18 21 0 3 6 9

Inu

nd

ati

on

de

pth

(m

)

Time (h)

Station J in Typhoon Megi


0

0.1

0.2

0.3

9 12 15 18 21 0 3 6 9

Inu

nd

ati

on

de

pth

(m

)

Time (h)

Station K in Typhoon Megi SimulationObservation

Strategy


E


Brick Theory

Coordinate the movable and un-movable facilities, software and hardware.

River regulation

Gate

Pumping station

Detention basin

Mobile pumps

Portable flood barrier


Polder dyke and pumping in the Budai Township, Chiayi County

Luan Temple

8/29 20:30 Polder accomplished 8/29 21:30 Pumps distributed and start pumping 8/30 11:00 Recession

Discharge direction

Polder 300 m, about 100 bulk bags 3 mobile pumps (0.3 cms / pump, total 0.9 cms)

4 mobile pumps (0.015 cms / pump, total 0.06cms)


Pilot projects of mobile flood barrier

County Location Length (m)

Yunlin Maming Village 4,800

Tainan Yongkang, Beimen, Madou Districts 200

Kaohsiung flexible 200

Pingtung flexible 480

Taitung Taimali, Luye, Beinan Township 320

Jinmen flexible 2,610

Total 8,610


Induce IOT into mobile pump

Bilateral communication, pump location and operation status Save electricity, low energy consumption Low price

4 G w i r e l e s s

m o n i t o r i n g

I O T m o d u l e

R e p o r t G P S l o c a t i o n

M o n i t o r b a t t e r y v o l t a g e

M o n i t o r p e t r o l e u m l e v e l

M a n u a l o p e r a t i o n b y e n g i n e e r

S t a t e o f p u m p s : i n i t i a t i o n / s t a n d b y / o f f l i n e

Conclusions Chapter. 4

50 Chapter 4. Conclusions

AWARENESS:

– High disastrous risks in Taiwan, because of the characteristics of natural environment.

– Risks increase under the impacts of climate change.

ACTIONS: Taiwan government has taken the action programs

– Integrate the national spatial planning to rethink the development philosophy in the urban and rural area.

– Integrate green and grey engineering.

– Apply technology to improve early warning and preparedness efficiently.

GOAL: Build a resilient home.

Source: Taijiang National Park


Test the mobile flood barrier. Apply the light and fast combination barrier as the second prevention line.

Taking the Maming Village in Yunlin County as an example, it raises the protection standard to 50 year recurrence interval without disturbing citizens’ daily life.

Mobile flood barrier: 50 years recurrence interval

SOBEK flood simulation

Current situation: 50 years recurrence interval

SOBEK flood simulation

Pumping station

Heighten the levee

21.4 ha flood, 0.52 m depth

No flood

Mobile flood barrier

Mobile flood barrier

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