Microsoft PowerPoint - TIWW-TJChang20190917.pptx Perspective of Urban Real-Time Pluvial Inundation
Prediction
1
Outline
Taiwan is vulnerable to various disasters Short-duration extreme rainfalls in Taiwan Challenge of Pluvial Inundation Prediction Novel Pluvial Inundation Modeling Real-Time Pluvial Inundation Prediction
2
3
Lloyd’s City Risk Index 2015-2025 (Oct. 2015) • Lloyd’s City Risk Index analyses the potential impact on the economic output
(GDP@Risk) of 301 of the world’s major cities from 18 threats.
• Taipei City is threatened by many kinds of disasters, especially suffering from wind storm, flood and earthquake.
Reference: http://www.lloyds.com/cityriskindex/threats
4
Reference: http://www.lloyds.com/cityriskindex/threats
• Seoul and Tokyo suffer the most from drought and tsunami, respectively!
Taiwan is vulnerable to various disasters
5
• Taipei is the top risk city among 301 cities.
Reference: http://www.lloyds.com/cityriskindex/threats
6
Avg. precipitation pre person (m3/person-yr)
Taiwan Philippines Japan India U.K. Italy U.S.A. France China Canada Australia Saudi Arabia World Avg.
North Area Central Area
South Area East Area
7
Taiwan is vulnerable to various disasters
8
Taiwan is vulnerable to various disasters
9
Taiwan is vulnerable to various disasters
10
The rainfall amount of hydrological events with 12-48 hrs duration in Taiwan is approaching to the world records. Now the intensity of short-duration events in Taiwan is more serious than ever.
Duration The World Rainfall Records Taiwan Rainfall Records Event 1 hour 356 mm 214.8 mm 1974/10/11 heavy rain events 19740706 3 hours 711 mm 476 mm 2002 Typhoon NAKRI 2002 6 hours 988 mm 645 mm 2010 Typhoon Megi 2010
12 hours 1374 mm 1157.5 mm 1996 Typhoon Herb 1996 24 hours 1909 mm 1748.5 mm 1996 Typhoon Herb 1996 48 hours 2654 mm 2361 mm 2009 Typhoon Morakot 2009 72 hours 3218 mm 2747 mm 2009 Typhoon Morakot 2009
Taiwan is vulnerable to various disasters
11
12
2015/06/14 Thunderstorm Most rainfall in 60 minutes is131.5mm (14:30~15:30)
Daan Dist. Gongguan Sta.
13
2017/06/02 Mei-Yu(plum rain) Taipei Metro Area Most rainfall in 1 hour : 112mm
Most rainfall in 3 hours : 238mm Most rainfall in 6 hours : 439mm
Short duration extreme rainfalls in Taiwan
14
2018/08/22~25 Tropical storm Southwestern Taiwan (Yunlin, Chiayi, Tainan, Kaohsiung, Pingtung)
Short duration extreme rainfalls in Taiwan Most rainfall in 1 hour : 121.5mm Most rainfall in 3 hours : 285.0mm Most rainfall in 6 hours : 384.0mm Most rainfall in 12 hours : 623.0mm Most rainfall in 24 hours : 822.5mm
15
2019/07/22 Thunderstorm Most rainfall in 60 minutes is136.5mm (15:20~16:10)
Daan Dist. Daan Park Sta.
16
Ranking Station Name Precipitation(mm) Date Weather System 1 Penghu() 214.8 1974/7/6 Southwesterly Flow 2 Suao() 200 2010/10/21 Typhoon Megi 3 Pengjiayu() 186 2002/7/10 Typhoon Nakri 4 Jiadong() 181.5 2017/7/29 Typhoon Nesat 5 Hengchun 168 2012/8/24 Typhoon Tembin 6 Xincheng() 167.5 2005/10/02 Typhoon Longwang 7 Kenting() 166.5 2012/08/24 Typhoon Tembin 8 Yuemei() 165.5 2002/03/26 Frontal 9 Tainan() 163.3 1947/7/29 Southwesterly Flow 10 Fongmei() 160.5 2004/09/12 Typhoon Haima 11 Dongjidao() 158 1987/5/18 Frontal 12 Fulong() 157.5 2004/10/25 Typhoon Nock-ten 13 Hengchun() 156.5 2005/9/23 Typhoon Damrey 14 Lili() 156 2003/08/03 Typhoon Morakot 15 Nanzhou() 155.5 2017/7/29 Typhoon Nesat
12 out of top 15 hourly precipitation records happened after 2000 5 out of top 15 hourly precipitation records happened after 2010
(1940-2018)
17
18
Reliability of quantitative small-scale real- time rainfall prediction
Accuracy and efficiency of small-scale real- time inundation simulation and prediction
19
How to forecast when three thunderstorm cells combine?
2015/06/14 Thunderstorm Rainfall in 60 minutes is 131.5 mm (14:30~15:30)
Challenge of Pluvial Inundation Prediction
Reliability of quantitative small-scale real- time rainfall prediction
20
Accuracy and efficiency of small-scale real- time inundation simulation and prediction
2019/07/22 Taipei Daan Park 15:30-15:50 86.5 mm 15:10-17:00 164 mm 15:10-16:10 136.5 mm
86.5mm/30min
21
Existing Flood inundation models
So far some commercial urban inundation models are available such as MIKE URBAN, INFORWORK, SOBEK, FLO-2D, HR Wallingford, TUFLOW, etc. However, in my opinion, their numerical accuracy on predicting urban inundation still remains an issue.
Total rainfall=127mm (3.5 hours) Maximum intensity=105mm/60min
Challenge of Pluvial Inundation Prediction
22
6 Doppler radar
Short duration Convective cell 3-hrs assessment
Rainfall Forecasting
Uncertainties come from
Challenge of Pluvial Inundation Prediction
Uncertainties come from
24
Uncertainties come from
25


Uncertainties come from
5
10
15
20
25
27
28
A. 2-D Flood Inundation Models , NTU-2DFIM
Levee breach flooding simulation in 2004
Urban flooding simulation in 2001
Novel Pluvial Inundation Modeling
30
Integratedly coupled SFM/OFM and coupled OFM/SFM for various land uses . (Chang et al., J Hydrology, 2015; 2017; 2018)
Novel Pluvial Inundation Modeling A. NTU-2DFIM
31
max 60-minute rainfall : 87mm
Novel Pluvial Inundation Modeling A. NTU-2DFIM Floods caused by clogging
Flood simulation result : 0% clogging rate
32
max 60-minute rainfall 87mm Min-sheng junior high school Sta.
max 60-minute rainfall : 87mm
Novel Pluvial Inundation Modeling A. NTU-2DFIM Floods caused by clogging
33
max 60-minute rainfall : 87mm
Floods caused by clogging
A. NTU-2DFIM
Floods caused by clogging
35
Instead of traditional FDM, FVM and FEM, Smoothed Particle Hydrodynamics (SPH) is developed for modeling river hydraulics and flood inundation.
SPH has the characteristics such as Lagrangian description, Particle approximation, Meshfree method for simulating fluid flows.
SPH formulation scalar:
f f W h V
x x
f f W h V
x x
W h V
x xf f
Novel Pluvial Inundation Modeling
surface)
Be intrinsically tracked based on the locations of particles Require finer meshes in the vicinity
of violent free surface
Forms of governing eqs.
Eulerian form (non-linear term exists)
Comparison between SPH and FDM
0
D d ( ) D d
0
d ( ) d
w f



37
(Chang et al., J Hydrol, 2011)
2D dambreak-induced flood and inundation
1D dam-break flow in a rough bumpy channel
15.5 m 10 m 6 m 6.5 m
G4 4 m 6 m
G10 3 m 7 m
G13 G20
h (m
h (m
38
Research Topic: Non-rectangular and non-prismatic open channel flows
Mixed regime flows in a trapezoidal prismatic channel Flow
Mixed regime flows in a rectangular non-prismatic channel
Novel Pluvial Inundation Modeling B. NTU-SPH
39
(Chang et al., J Hydrol, 2014, 2015) Single solitary wave
Two solitary waves
40
Research Topic: 2D open channel flow simulations in complicated geometries Uniform rainfall over a 2D plot with complex topography
A 1D–2D coupled SPH-SWE model
Novel Pluvial Inundation Modeling B. NTU-SPH
(Chang et al., J Hydrol, 2016, 2017)
(Chang et al., Advances in Water Resources, 2018)
41
Novel Pluvial Inundation Modeling
(Chang et al., J Hydrol, 2019)
NTU-CA is an innovative flood inundation modelling tool, which is programmed with the graphic hydraulic concept to quickly detect floods in few seconds or minutes rather than hours or days.
• Rapidly estimates flood extents and depths from many sources of flooding, including coastal, fluvial, pluvial, surface water and sewer flooding.
• Combining surface and subsurface flow using EPA SWMM 5.1.
• Enables flood mapping at local, regional and national scales. • Real-time flood mapping when linked to forecast rainfall.
Novel Pluvial Inundation Modeling C. NTU-CA
43
Total rainfall (mm) Duration(hour) simulation
time(min) 2014/05/20 haevy rain 73 418.5 12 13.7 2014/06/25 haevy rain 71 103 6 5.5 2015/06/07 haevy rain 89.5 132.5 5 4.6 2015/06/14 haevy rain 131.5 193 5 5.4 2015/07/23 haevy rain 112.5 137.5 4.8 4.8
2015 Typhoon Soudelor 114 316.5 16 17.5 2015 Typhoon Dujuan 85.5 420.5 24 23 2016/06/07 haevy rain 114 141 8 8.3 2017/06/02 haevy rain 111 334.5 6 6.7 2018/09/08 haevy rain 138 240.5 9 9.4
Novel Pluvial Inundation Modeling C. NTU-CA Fast and accurate simulations of real flood events
44
Real-Time Pluvial Inundation Prediction
Background • To reduce flooding disasters, Public Works Department of Taipei
City Government and National Taiwan University have together executed a scientific research plan that conducts real-time flooding assessment and early warning in Taipei City.
• The rapid Cellular-Automaton urban flooding model developed by National Taiwan University (NTU-CA) is used to implement the flooding assessment.
Flooding Assessment and Early Warning
Real-Time Pluvial Inundation Prediction
Real-Time Pluvial Inundation Prediction
Real-time flood projection system to be tested in Tokyo (S-uiPS) A team from Waseda University, the University of Tokyo, and the Remote Sensing Technology Center of Japan devised a computer system that predicts flood levels 30 minutes into the future in Tokyo’s 23 wards in real time. Its stable operation is expected to be ready by the Tokyo Olympic Games in 2020.
Building Road
NTU-CA • Real-time flooding map that considers a
forecast rainfall as an input. A 2-hour-ahead and radar-based forecast rainfall estimation combined with 4-hour observed rainfall data are integrated as an rainfall input to conduct a 6-hour flooding assessment in Taipei city.
Real-Time Pluvial Inundation Prediction
49
• The computing time of a case of a 6-hour flooding assessment in Taipei City is almost within 30 minutes, and the flood forecasting is updated every 30 minutes.
• When floods come, the flooding information such as flooding extents can be provided before 90 minutes.
Real-Time Pluvial Inundation Prediction
51
X band MP radar QPF 250 m/5min
S band radar QPF 1250 m/10min
52

53