flood forecasting model user manual
TRANSCRIPT
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Flood Forecasting Model
User Manual
Ethiopian Ministry of Energy and Water Resources
Prepared by
Addis Ababa University
Civil Engineering Department
2010
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Table of Contents
Introduction ................................................................................................................................... 30
1. Installation............................................................................................................................. 32
1.1. Requirements .................................................................................................................. 32
1.2. Installation Procedure ..................................................................................................... 32
Data Structure ........................................................................................................................... 32
The user interface setup ........................................................................................................ 35
Computer Programs...................................................................................................................... 35
The User Interface ..................................................................................................................... 37
Table of Contents .......................................................................................................................... 31
Table of Figures ............................................................................................................................ 31
Table of Figures
Figure 2 Setting the Hec-Hms hydrologic model program ........................................................... 34 Figure 3 Hec-Hms open file dialog box ........................................................................................ 34 Figure 4 General workflow for forecasting .................................................................................. 36 Figure 5 The main dialog .............................................................................................................. 37 Figure 6 sample comma-delimited text file showing the rainfall input ........................................ 38 Figure 7 Input Dialog box ............................................................................................................. 38 Figure 8 file selection dialog ......................................................................................................... 39 Figure 9 Running the Hec-Hms Rainfall Runoff model ............................................................... 39 Figure 10 The rainfall input shown in the Hec-Hms program ...................................................... 40 Figure 11 The Runoff output from the hec hms model ................................................................ 40 Figure 12 Hec-Ras Unsteady flow analysis dialog box ................................................................ 41 Figure 13 The Unsteady flow dialog box ..................................................................................... 42 Figure 14 The Unsteady flow dialog box ..................................................................................... 43 Figure 15 select the maximum water surface profile and optionally water surface profiles for other time ...................................................................................................................................... 43 Figure 16 Hec-Ras output showing a longitudinal section of a river and the water elevations at selected instantaneous time frames ............................................................................................... 44 Figure 17 Export an SDF file for processing in GIS .................................................................... 45 Figure 18 Importing the SDF file into GIS using Hec-GeoRas extension ................................... 45 Figure 19 Layer setup dialog box in Hec-GeoRas ........................................................................ 46 Figure 20 Sample map showing inundation depth categories ...................................................... 49
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Introduction
This manual describes the flood interpreter computer program and its user interface. The purpose
of the user interface is to help the user prepare the forecasted rainfall for input in the rainfall
runoff models (HEC-HMS) and of hydraulic models ( Hec-Ras) of the concerned catchments i.e.
Rib, Gumara, Dirma and Megech smoothly by automatically feeding the necessary input data
from weather models and other observed data and also to ease the transfer of enormous data
between the different models which otherwise would be too cumbersome to do manually and
difficult to perform error free in a short time.
1. Installation
1.1. Requirements
This computer program has been tested on an XP operating system. With Pentium-4 processor
Ram - 256MB
Hard Disk - 20GB
The computer program is developed using visual basic.net programming language and is capable
of performing on almost all computers on which the Dot-Net framework of version 3.5 and
above is installed.
1.2. Installation Procedure
Data Structure
The rainfall runoff models and the hydraulic models need to be copied on the host computer for
the proper functioning of the user interface. Other files are needed for the interoperation of these
models and for temporary storage of data. The following figure shows the general File Directory
Structures that need to be copied in the C:\ drive of the user’s computer.
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Once these files are copied in the C:\ Directory, the next step is to set the Hec-Hms rainfall
runoff modeling program for easier operation. For this go to the Tools-> Program Settings menu
and set Project directory to be “C:\filesforFloodInterpretor\HmsBasinModels\Tana\ “ and also
make sure the “Automatically close progress window when successful” check box is checked as
shown on the following figure.
FilesforFloodInterpretor
Commands
FlowData
HmsBasinModels
HydraulicModels
Settings
HourlyData
Settings
OofFInterpreter
DssUTL.exe
Figure 1 File Directory Structures
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Figure 2 Setting the Hec-Hms hydrologic model program
Once the settings are set, opening a rainfall-runoff model for a particular basin is easier
Figure 3 Hec-Hms open file dialog box
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The user interface setup
The setup file for the Flood Interpreter software is named Gorfu. The setup file first checks if the
Dot-Net Framework is already installed and if it is not, it will automatically start to install.
Once the Dot-Net framework and the computer program is installed, it can be accessed through
Start Menu -> Hela -> Gorfu
Computer Programs
Rainfall estimation, rainfall-runoff modeling, hydraulic modeling and visualization computer
programs are used sequentially in this flood forecasting scheme. Large amount of data has to be
communicated among these computer programs and also control settings of each computer
program have to be done correctly to achieve accuracy.
The purpose of the user interface computer program is for the forecasting to be done and
communicated in an acceptable time frame to provide the end users (the population that will be
affected) with enough lead time before disaster (flood) strikes. Moreover, the routine and
relatively cumbersome settings of the different computer programs have to be automated to
guard against possible human errors. Therefore, the user interface and the accompanying
computer program development are essential components in this project.
The user interface is coupled with programming for easier, error free data interoperability, for
correct settings of the intricate computer programs that would otherwise need long hours to do
manually and for a proper sequence of simulation and processing runs.
The computer program developed along with the user interface can help an average hydraulic
engineer or hydrologist to undertake the forecasting responsibility easily.
The general workflow, computer program models and the necessary data are described in the
following figure.
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Figure 4 General workflow for forecasting
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The User Interface
What the user interface computer program of this flood early warning system does is, change the
format of the forecasted rainfalls, which are retrieved in a tab delimited text format, and feed it in
the Hec Hms’s data storage database (Hec-Dss database) and set the Hec Hms’s simulation
controls.
Initially, a general direction is shown for the user in the main dialog box. Three buttons at the
bottom of the user interface are also used to guide the user through phases of the forecast
process.
Figure 5 The main dialog
To start the process of forecasting, the user needs to provide data from the weather models that is
retrieved in a text file containing data in a tab delimited format and the name of the file being the
start of the simulation date.
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Figure 6 sample comma-delimited text file showing the rainfall input
The observed downstream water level is also typed in the “Lake Tana Level” text box so that the
computer program feeds it in the Hec-Ras computer Models Hec-Dss database to be used as the
downstream boundary condition for the hydraulic simulation. Please refer to the Hec Ras user manual for further explanation.
Figure 7 Input Dialog box
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Figure 8 file selection dialog
Once the rainfall and water level boundary conditions are entered, the run Hec-Hms button is
enabled.Open the rainfall runoff model file named “Tana” and run the model, as shown in the
following figure clicking the buttons as shown using numbers. Please refer to the Hec Hms user manual for further information
Figure 9 Running the Hec-Hms Rainfall Runoff model
1
2
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Figure 10 The rainfall input shown in the Hec-Hms program
Figure 11 The Runoff output from the hec hms model
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From the above hydrograph we can see what the peak times will be in this case, the maximum
flow will be at
On 08 Sep at 14:00;
On 09 Sep at 02:00;
On 10 Sep at 07:00
After this the run Hec-Ras button in the user interface is enabled and when it is clicked the Hec-
Ras hydraulic modeling program is initiated. To run the unsteady models:
First click unsteady run button to open the unsteady flow analysis dialog box. And set the
simulation start and end date.
Figure 12 Hec-Ras Unsteady flow analysis dialog box
1. Click the run unsteady button on Hec-Ras main interface
2. Set the simulation time. Using the current date as the start date and adding 3 day on
the start date for a forecast of 72 hours.
3. Click the compute button to allow Hec-Ras to calculate the water levels.
4. Save and exit.
1
2
4
3
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Figure 13 The Unsteady flow dialog box
Then open the unsteady flow dialog box and set the initial flow data. Note that the boundary
conditions' positions are set only once but the flow data for it is read from a Hec-Dss database
1
2
3
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Figure 14 The Unsteady flow dialog box
Click on the unsteady run button on the hec ras main dialog box to run the analysis.
Figure 15 select the maximum water surface profile and optionally water surface profiles for other time
1
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0 5000 10000 15000 20000 25000 30000 350001780
1790
1800
1810
1820
DirmaUnsteady Plan: Plan 08 08/10/2010
Main Channel Distance (m)
Elev
atio
n (m
)
Legend
WS Max WS
WS 07SEP2010 0800
WS 08SEP2010 0800
Ground
Dirma River Dirma
Figure 16 Hec-Ras output showing a longitudinal section of a river and the water elevations at selected instantaneous time frames
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Export an SDF format file from File->Export to GIS for processing and visualization in GIS.
Figure 17 Export an SDF file for processing in GIS
To use the exported SDF file in ArcGis, it must be converted to an XML file using “convert SDF
TO XML” button Hec-GeoRas toolbar use.
Figure 18 Importing the SDF file into GIS using Hec-GeoRas extension
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Use the Ras Mapping button on Hec-GeoRas toolbar to setup layers
Figure 19 Layer setup dialog box in Hec-GeoRas
The layer setup is used to
Name the current analysis
Set The GIS import file (the converted xml file) from Hec Ras
The terrain data
The output directory (which should be connected-to in ArcCatalog)
The raster grid size (which should be set around 10 to 20 from analysis time, storage
space and accuracy considerations). use 10 for daily forecast operations. Please refer to the Hec-GeoRas user Manual for more information
Click the following buttons from the Ras Mapping menu in sequence.
Read RAS GIS EXPORT file
Inundation Mapping -> Water Surface Profile
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Inundation Mapping -> Flood Plain Delineation Using Rasters
This will set the maximum flood depth that will be experienced in the flood plain in the coming 3
days. To interpret this information on how it may affect the population, we categorize it as
D < 0.5
0.5m < D < 1.0m
And D > 1.0 m
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1. Right click the “d Max WS” layer and choose the Properties menu
Choose “Symbology” Tab
2. Choose Classified as shown in number 2
3. Open the combo box and set it to 3
4. Set Break values of 0.5, 1.0 and leave the maximum value in the list as it is.
5. Click the “Ok” button
6. Double click the color swatches and set the top to green; the middle to yellow; and
the bottom swatch to red.
This will indicate how dangerous or tolerable the flood depth will be on different locations on the
map. To see the effect on local population,
Import the layers showing
The Kebele administrative boundary
Settlement areas
Roads
1 2 3
4
5
6
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Coupled with the information which shows the peak times of the flood, the population and
officials can prepare for it or make decision to evacuate.
Figure 20 Sample map showing inundation depth categories
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Although the map in figure above is a good indicator of what areas will be affected and by how
much, it may not be easy to transfer to the local population and local Kebele and Woreda
officials. Therefore the map needs to be synthesized in a form of a table as shown below.
Maximum flow will be at Dirma 08 Sep 14:00; 09 Sep 02:00; 10Sep 07:00
Dirma River
Kebele Percent Inundation Remark ( Affected Settlements)
< 25
%
25 50 75 100 Flooded Area
Aberjeha
Dihana Wuha
√ - - - - May affect areas up to 500m from
the river
Serba Deblo - - Yes - - Settlements Seraba Maryam and
Dablo Michael may be affected
Chenker
Chiristos
√ - - - - May affect areas up to 1km from
the river
Meskele
Chirstos
√ - - - - May affect areas up to 1km from
the river
Janqua Mariam
na J/Abreham
√ - - - - May affect areas up to 1km from
the river
Gebeba Chilo √ - - - - May affect areas up to 500m from
the river including some settlements