This document summarizes the transfer of a 2D flood model from SOBEK to Delft3D FM for potential inundation mapping in Taiwan. It describes how geometry, hydrologic, and hydraulic data were transformed from the original SOBEK model to the new Delft3D FM model. A case study application to the Yanshuei River basin in Tainan, Taiwan is presented, showing Delft3D FM can simulate flooding from Typhoon Megi more efficiently than the original SOBEK model. Next steps proposed include additional model testing with high-resolution data and developing tools to automate the model transfer process.

1. Copyright ©2016-2019 FondUS Technology Co., Ltd.
2019 Delft3D - User Days
2019/11/11
From SOBEK to Delft3D FM 2D model transfer case for
the potential inundation map in Taiwan
Jhih-Cyuan Shen
FondUS.inc ,Taiwan
Shih-Hao Chiu
Taipei Tech ,Taiwan
Delft3D - User Days

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# Agenda
✓ Introduction
✓ SOBEK Model Development in Taiwan
✓ Delft3D FM Transformation
✓ Case of Delft3D FM
✓ Next steps and Suggest

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Introduction
• The Flooding rainfall type in Taiwan
• Typhoon (3~4 per year)
• Short-duration extreme rainfall
• Monsoon (May and Oct )
2
Potential Inundation Map
CWB CWB
NFANFA

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Introduction
3
Data survey and collection
Building model
Scenario
Time series and parameters
Simulation
Results release and
publish
Verification
and validation
Model update
and maintenance
Potential Inundation Map
Work flow
Realtime of 2D Simulation

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23-24, August, 2018
Tropical Depression
Town Area Average Rainfall
Accumulated: 780-950mm/2day
Maximum: 92-121mm/hr
Chiayi Tainan
KaohsiungPingtung
Chiayi
Pingtung
Kaohsiung
Tainan

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13, August, 2019 Tainan
Emergency System Respond flooding information 139 points
IoT Flood senors
Rain Gauge:
6hr 245mm
3hr 194mm
1hr 81.5mm

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13, August, 2019 Tainan Case
6
• Flood Pond

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SOBEK Model Development in Taiwan
7
26 Rivers
SOBEK 1D+RR
± 72hr ( 7/24 )
■Forecast Basin
17 Regions(country or city)
SOBEK 1D+2D+RR(SCS)
Potential Inundation Map
2014~2016
■Model Region
2005~2014

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SOBEK Model Development in Taiwan
8
2016
Taichung
2017
Tainan
2018
Kaohsiung
Pingtung
Yilan
2019
Taoyuan
 Realtime of 2D SOBEK Simulation
 FEWS-Taiwan (Delft-FEWS)
 Live system MC: 2VM FSS: 32VM
 40M*40M (20M*20M)

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Why We Want to Transfer SOBEK to Delft3D FM 2D model
• High-resolution DEM data provide
• 40m→20m→10m→5m→1m
• Computing performance
• SOBEK only use 1 core ( Base on CPU clock rate )
• Server CPU is more expensive than PC CPU
• More Regions Data need to Provide
• Parallel computing
• Flexible Mesh Grid
9

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Delft3D FM Transformation
10

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Delft3D FM Transformation
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All geometry data(Network node and Branch)
• Cross section
• Watergate
• Pumping Station
• River bank
• Flood Pond
• Irrigation and Drainage Data (Manhole)
• Digital Elevation Model (2D Grid)
Hydrology and Hydraulic data
• Model parameter
• Rainfall Runoff, Manning N
• Time Services
• Tide, Water level, Discharge
• Structure information
• Pump, Reservoir, Manhole
SOBEK Delft3D FM

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Delft3D FM Transformation
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Source and Sink
Delft3D FM 2D has no RR function now. So we run RR in SOBEK model
first and get runoff value from it.
Digital Elevation Model
In Delft3D FM, DEM is defined in two parts, simulation Cell and Elevation.
Boundary Condition
In Delft3D FM there are two kind of boundary condition, water level
in river and coast.

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Delft3D FM Transformation
Item Shape File Parameter Grid
Type Boundary
(line,point)
Source & Sink
(RR-Node)
Boundary Source &
Sink
Simulation
Cell
Elevation
File *.pli *.bc *.tim *.nc *.xyz
Remarks Point
Line
Water Level
Discharge
Discharge cell area ,
cell average
level.
13
Data format in Delft3D FM

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Case of Delft3D FM
• Study Area – Tainan ,Yanshuei-chi Drainage System
14
Simulation Area

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Case of Delft3D FM
15
Source and Sink
-RR node
-Discharge
Boundary Condition
-Line
-tide
Simulation Cell
- Elevation
-Cell

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Case of Delft3D FM
16
Megi Typhoon
From: 2016/09/27 06:00
To: 2016/09/29 02:00
Rainfall
Maximum: 85 mm/hr
Accumulated: 485 mm-24hr
Wind speed
Maximum: 250 km/hr

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Case of Delft3D FM
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Model Property SOBEK Delft3D FM
Simulation Cell Num 270,512 (each grid for 20m*20m)
Calculation Spend 260 min 53 min

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Case of Delft3D FM
18
5M HyDEM(HydroDEM)5M DSM20M DEM
5M HyDEM(HydroDEM)
HydroDEM
Keep
-Building elevation
-Hydraulic structures
Add
-Dike elevation line
Remove
-Cross-river structure

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Next steps and Suggest
• More case testing
• For different type of Flexible Mesh Grid
• QuadTree, TIN, Curvilinear
• HydroDEM
• High-Resolution 1m and 5m
• Different Regions models
• Transfer tools and SOP documents
• Batch script tools for the SOBEK to Delft3D FM
• Transfer SOP documents
19
High Resolution 2D grid test
QuadTree grid TIN grid Curvilinear grid

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Thank you for your interest!
Share and Cooperation
FondUS Technology Co., Ltd. https://www.facebook.com/fondus.inc
Jhih-Cyuan Shen coop.shen@gmail.com
Shih-Hao Chiu andy950702@gmail.com