Flood Management Strategies - in Taiwan - Extreme Rainfall Dr. Chien-Hsin Lai Director-General
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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
1 Where we live
2 What we think
3 How we do
4 Conclusions
2
Chapter. 1 Where we live
Geographic location of Taiwan
Russia
Mongolia
North
Korea
Japan
South
Korea
China
Myanmar
Laos
Taiwan
Thailand
Philippines
Vietnam
Malaysia
Indonesia 4
5 Chapter 1. Where we live
Country Date
FLOOD Casualty
Taiwan 0823 7 deaths, 8492 evacuations
Philippine 0812 54,000 evacuations
Myanmar 0731 11 deaths, 120,000 evacuations
Dam Break
Laos 0723
27 deaths, 1126 missing
Japan 0705 105 deaths, 87 missing
Vietnam 0625 7 deaths, 12 missing
China 0507 6925 evacuations
Malaysia 0104 9000 evacuations
Asian events occurred in 2018
6 Chapter 1. Where we live
The extreme events
are equivalent to the world records
Réunion
France
Taiwan record (mm)
(2007)
World record (mm) Pingdung
up to 2009 (2009)
Pingdung
rainfall (2009)
Cherrapunji
Storm event
(mm/hr) India
(1995)
2016/ Nesat 181 Pingdung
Réunion
France
(2009)
2017/ 06.01 132 (1966)
2018/ 08.23 121
Kauai
USA
Penghu
(1956)
(1974)
1 hr 1 day 2 day 3 day
Source: Taiwan WRA, 2017
7 Chapter 1. Where we live
Short concentration time
Concentration
River time (hr) Comparison of River Slope
Danshuie 15.4 Taiwan’s Rivers
Jhuoshuei 18.35
Zengwun 15.44
Elevation (m)
Rhine River
Yanshuei 14.55 (Europe)
Gaoping 14.45
Japan’s River
Lanyang 7.13 Colorado River
(USA)
Hualien 7.24 Mekong River
Mekong 458 (Asia)
Rhine 342
Estuary
Colorado 94 Distance (km)
Source: River planning report.
8 Chapter 1. Where we live
Typhoon paths in 2013
Threats by typhoons
Average: 3.5 typhoons / year
Number of typhoon attacks during 1911-2017
Definition of attack:
No typhoon 1. Typhoon center Typhoon Trami
landing
1 typhoon
2. With no center Typhoon Cimaron
landing, but cause
disaster on land
2 typhoons
Typhoon Usagi
3 typhoons
4 typhoons
Typhoon Fitow
5 typhoons
6 typhoons
7 typhoons
Picture: Lin; source: CWB
9 Chapter 1. Where we live
Hazards induced by extreme events
Increased
Total rainfall Reduced volume
Area Event area of
(mm) percentage (%)
landslide (Ha)
Shihmen Reservoir 2004Typhoon Aere 1,022 326 12.2
Zengwun Reservoir 2009Typhoon Morakot 3,058 1,126 9.0
??
Shihmen
曾文水庫 Reservoir
Line/Scatter Plot 3
Landslide area (ha)
石門水庫
Line/Scatter Plot 1
Zengwun Reservoir 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
賀
921
921
桃 娜 艾 艾 海 六 柯 卡 莫 凡 南 蘇 蘇 麥 蘇 尼 尼
Before Typhoon Aere
After Typhoon Toraji
After Typhoon Krosa
After June storm
After Typhoon Nakri
After Typhoon Herb
After Typhoon Kalmaegi
Before 921 earthquake
After Typhoon Haitang
After Typhoon Morakot
After Typhoon Nepartak
After Typhoon Matmo
After Typhoon Soudelor
After Typhoon Saola
After Typhoon Nesat
After Typhoon Nanmadol
After Typhoon Aere
After Typhoon Soulik
After Typhoon Fanapi
After 921 earthquake
伯 芝 克 利 利 棠 九 羅 玫 拉 那 瑪 拉 力 德 迪 伯 莎
颱 大 大 颱 莉 颱 颱 颱 豪 莎 基 克 比 都 颱 颱 姆 勒 特 颱
風 地 地 風 颱 風 風 風 雨 颱 颱 颱 颱 颱 風 風 颱 颱 颱 風
後 震 震 後 風 前 後 後 後 風 風 風 風 風 後 後 風 風 風 後
前 後 後 後 後 後 後 後 後 後 後
10 Chapter 1. Where we live
Threaten by compound disasters
Highly
Flooding
prone area
71.5%
1.4% 21.5%
1.4%
Highly Highly
Debris Flow Landslide
prone area 8.5% prone area
8.4% 38.0%Chapter. 2 What we think
12 Chapter 2. What we think
Highly concentrated population in the cities
Population growth rate (%)
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
Source: Statistical Yearbook of Interior- Department of statistic, Ministry of Interior (2018)13 Chapter 2. What we think
Urbanization reduces river space
Source: Westerner in Taiwan (KP17)
City Urban area(Ha) River area (Ha) (%)
Taipei 27,180 1,794 6.614 Chapter 2. What we think
Taiwan is threaten by climate change
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%).
Variation of storm days
Near future Mid of century End of century Near future Mid of century End of century
Variation (%)
Variation (%)
central north
Near future Mid of century End of century Near future Mid of century End of century
Variation (%)
Variation (%)
south east15 Chapter 2. What we think
Resilient City
Extreme event Resilient community, resilient city Flooding
• Mitigate the disaster level in the system;
• Reduce the recovery time of the system; unavoidable
• Enhance the learning capacity during the disaster
Green engineering
• Build the detention facility
non-structural
Protection by
• Building management and disaster prevention
• Green infrastructure
• National spatial planning and reallocation
Rainfall scale
• Flood insurance
Only protect for the usual events (high occurrence
probability)
•Protection standard for farm drainage
– 10 years recurrence interval，1-day average
Gray engineering
structure
Protection by
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
Normal – 10 year recurrence interval
event Source :Pao-Shan Yu, Briefing on the flooding symposium in the Mino district of Kaohsiung City(Aug 12, 2018)Chapter. 3 How we do
17 Chapter 3. How we do
Strategy
A18 Chapter 3. How we do
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)19 Chapter 3. How we do
Road effects Problem of water blocked by roads
Guo-Gou Village20 Chapter 3. How we do
Road effects Embankment effect
Village protection
facilities
Wang-liao Villiage
Elevated road21 Chapter 3. How we do
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 detention22 Chapter 3. How we do
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- Denver road discharge
interchange detention pond
Reduce the elevation of divisional Set the detention pond in
island to increase water storage system interchange
Provincial Highway 61 Shalu Interchange23 Chapter 3. How we do
Strategy
B24 Chapter 3. How we do
Runoff Distribution
An Extreme Precipitation will exceed the
capacity of rainwater sewer systems and
cause flooding.25 Chapter 3. How we do
Runoff Distribution
Green
land
River
School
Park
Parking
lot
The runoff can be distributed over the public
spaces, such as rivers, parks, parking lots,
schools, and green spaces.26 Chapter 3. How we do
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.
Runoff Distribution Outflow regulation
purpose
Response to the runoff Response to the runoff
increase by climate change increase by development
obligor Government Development sector
range
Specific watersheds & Development case beyond
basins by declaration specific scale
method Prior to public land Applied in the site area
New constructed public Apply the detention pond,
practice facility with detention low impact practice, etc.
function，ex: park, road on site to reduce runoff
drainage, etc.
Resilience27
Maple Garden
“Maple Garden” in Taichung City has
functions of flood detention, drainage and
recreation.
Constructed in 2012; total storage capacity
is 200,000 m3.
Source：Taichung City Government28
Benhe Detention Park
“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.
Source：Kaohsiung City Government29 Chapter 3. How we do
Outflow Regulation
Urbanization increases flood risk
The land developers construct the detention basins and Low Impact
Development facilities.
post-development +
pre-development post-development flood mitigation facility
outflow outflow outflow
29Donghu Detention Basin
In Dali Software Park
Completed in 2014
Total storage capacity of 8,000 M3
Reduce flood risk of surrounding 10 ha,
and protect 1700 residences
Source：Taichung City GovernmentFlood detention Basin in
Pinglin Forest Park
Completed in 2015
Total storage capacity of 32,000 M3
A multi-purpose park with ecological,
landscape, flood detention and recreation.
Source：Taichung City Government32 Chapter 3. How we do
Strategy
C Detention on site33 Chapter 3. How we do
Land use fits in spatial planning
Others
Building
Land use Area(Km2) (%)
Hydrological Agriculture 874 67.7
4.5%
Forest 104 8.0
Traffic Traffic 80 6.2
Hydrological 58 4.5
Agriculture
Forest Building 103 8.0
67.7%
Others 73 5.6
Total 1292 100
*land use distribution in Yunlin County
*Source: department of land administration, MOI34 Chapter 3. How we do
Case study in Loisach River, Germany
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.
Levee
Flood area Village
Levee
Source :Bavarian State Water Authority, 2010 Bavarian Rural Development and Water Management Mission35 Chapter 3. How we do
Detention on site
Apply the idle/ fallow farm
and fishing pond to share
the flood storage during
storms.
Wa-Yao Village
Flood simulation of 100-year return period
Modified
Flooded area 4.6 ha, flooding
depth 0.4 m in village No flooding in village Farmland 80 ha36 Chapter 3. How we do
Strategy
D37 Chapter 3. How we do
Early warning
Rainfall in Gangshan station on Sep. 19 in 2010 (Typhoon Fanapi )
Flooding at 15:00 at the Rescue team arrive
Rainfall (mm)
200 nursing home at 20:00
雨
量 Flood prediction
100
(
get 3hr earlier for 3Hours
毫 response
米
)
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 125 226 3 27 4 285 29
6
Get 8 hrs for response
Now: evacuation beforehand Before: wait for rescue38 Chapter 3. How we do
Improve the rainfall radar system
Provide the higher resolution of rainfall spatial distribution
Before After
resolution：1.3Km x 1.3Km resolution：250m x 250m
The maximum
The maximum
rainfall
rainfall observed by
observed by
the old radar
Linyuan radar
22mm/hr 23mm/hr39 Chapter 3. How we do
Application of radar data for precipitation monitoring
0908 storm event
Spatial and temporal distribution of
rainfall along Xinyi Road
(from east to west)
MRT Dongmen station Sec. 1, Xinsheng S. Rd. Daan Forest Park
Flooding from east to west40 Chapter 3. How we do
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.
Future precipitation forecast Typhoon Megi in 2016
by CWB
INPUT41 Chapter 3. How we do
Flood prediction online system
Automatic, real-time and dynamic
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.
Flood warning, flood
Results exhibition Exhibition depth, flood duration
Machine
Big data database learning
Big
data
AI42 Chapter 3. How we do
Risk assessment for watershed
Risk analysis provides well information to
prevent and mitigate disasters
曾
文
二
橋
曾
文
一
橋
大 大
Liaobu levee (high risk)
內 內
八 十 中
dam failure simulation 號
橋
號
橋
正
橋
玉
豐
大
橋
Mashan Taitie
Bridge Bridge Danei
Guoxing Xigang Bridge
Bridge Bridge Erxi
Bridge
Section 1 Section 2 Section 3 Section 4 Section 5 Section 6
Close to
Not satisfied to waterway or High liquefaction Basis depth is
project flood scour directly potential layer not sufficient43 Chapter 3. How we do
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%.
0.6 0.3
Inundation depth (m)
Inundation depth (m)
Station D in Typhoon Megi Station I in Typhoon Megi
Simulation Simulation
0.4 Observation 0.2
Observation
0.2 0.1
0 0
9 12 15 18 21 0 3 6 9 9 12 15 18 21 0 3 6 9
Time (h) Time (h)
0.5 0.3
Inundation depth (m)
Inundation depth (m)
Station J in Typhoon Megi Station K in Typhoon Megi
0.4 Simulation Simulation
Observation 0.2 Observation
0.3
0.2
0.1
0.1
0 0
9 12 15 18 21 0 3 6 9 9 12 15 18 21 0 3 6 9
Time (h) Time (h)44 Chapter 3. How we do
Strategy
E45 Chapter 3. How we do
Brick Theory
Coordinate the movable and un-movable facilities, software and
hardware.
River regulation
Portable flood barrier
Detention basin
Pumping station
Mobile pumps
Gate46 Chapter 3. How we do
Polder dyke and pumping in the Budai
Township, Chiayi County
3 mobile pumps
(0.3 cms / pump, total 0.9 cms) Polder 300 m, about 100 bulk bags
8/29 20:30
Polder accomplished
8/29 21:30
Pumps distributed and
start pumping
8/30 11:00
Recession
Discharge
direction Luan Temple
4 mobile pumps
(0.015 cms / pump, total
0.06cms)47 Chapter 3. How we do
Pilot projects of mobile flood barrier
County Location Length (m)
Yunlin Maming Village 4,800
Yongkang, Beimen,
Tainan 200
Madou Districts
Kaohsiung flexible 200
Pingtung flexible 480
Taimali, Luye,
Taitung 320
Beinan Township
Jinmen flexible 2,610
Total 8,61048 Chapter 3. How we do
Induce IOT into mobile pump
Bilateral communication, pump location and operation status
Save electricity, low energy consumption
Low price
Report GPS location
Monitor battery voltage
4G wireless
Monitor petroleum level
monitoring
IOT module
Manual operation by engineer
State of pumps:
initiation/ stand by/offlineChapter. 4 Conclusions
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
52 Chapter 3. How we do
21.4 ha flood, 0.52 m depth
Mobile flood barrier
Test the mobile flood barrier. Apply
the light and fast combination barrier
Current situation: 50 years
as the second prevention line. recurrence interval
Taking the Maming Village in Yunlin SOBEK flood simulation
County as an example, it raises the
No flood
protection standard to 50 year
recurrence interval without disturbing
citizens’ daily life.
Mobile flood barrier Pumping Heighten
station the levee
Mobile flood barrier:
50 years recurrence interval
SOBEK flood simulationYou can also read
