D43011925

Marina Mazlan et al Int. Journal of Engineering Research and Applications www.ijera.com
ISSN : 2248-9622, Vol. 4, Issue 3( Version 1), March 2014, pp.19-25
www.ijera.com 19|P a g e
Generation Of Flood Inundation Model – General Approach And
Methodology
Marina Mazlan2
, MohdAdibMohammed Razi1
, MohdShalahuddinAdnan1
,
MustaffaAnjangAhmad1
,KhayrulApriAmsoSuis2
.
1
Senior Lecturer, Faculty of Civil and Environmental Engineering, UniversitiTun Hussein Onn Malaysia,86400
Parit Raja, BatuPahat, Johor, Malaysia.
2
Post-graduate student, Faculty of Civil and Environmental Engineering, UniversitiTun Hussein Onn Malaysia,
86400 Parit Raja, BatuPahat, Johor, Malaysia.
Abstract
This paper presents in general the approach, methodology and applied practice for the generation of flood
inundation model. The generation of the model cover on: (1) data availability, (2) methodology, (3) flood
modeling using the one-dimensional (1D) and two-dimensional (2D) hydrodynamic model, and (4) generation
of flood inundation modelof integration of hydrodynamic model and flood mapping approach. The Sembrong
River hydrodynamic model, Sembrong River flood mapping, and Kota Tinggi Flood Inundation Modeling are
presented as an example.
Keywords: Hydrodynamic model; Flood map; Flood inundation map; Flood forecasting; Flood Risk
Assessment.
I. INTRODUCTION
In the past decades, lots of damages
occurred, directly or indirectly, by flooding. In fact, of
all natural hazards, floods pose the most widely
distributed natural hazards to life today.
A flood inundation model will be developed
using hydrodynamic model and flood mapping
approach. Calibration and validation of the model will
be carried out using collected and historical
hydrological data.
Thus the need of flood inundation modelling
has increased in line with model developments and
increased computational resources, but the possibility
that simpler models may provide similar levels of
predictive ability has not actually been considered [5].
2-Dimensional (2D) hydrodynamic models
are best employed in conjunction with a Digital
Elevation Model (DEM) of the channel and floodplain
surface [4]. In conjunction with suitable inflow and
outflow boundary conditions, allows the water depth
and depth-averaged velocity to be computed at each
computational node at each time step. The recent
advancement in the computer technology enables the
computer models to be developed by modelling the
river system and perform a flood simulation,
prediction can be made to avoid unexpected flood and
remedial action can be taken earlier [4].Flood is well
known as a silent killer. The damages caused by flood
might cost a billion dollars. Damages widely
occurred, to infrastructures, properties, in fact might
as well capable of killing living things.
Generally, this paper presents the approach and
methodology for data collection, modeling and
integration of hydrodynamic model and flood
mapping. Findings from previous study carried out by
reference [4], at Kota Tinggi catchment area are
presented as examples of the application practices for
the generation of flood inundation model map in
Johor.
II. APPROACH AND METHODOLOGY
Generally, the approach and methodology to
generate a flood inundation map can be illustrated as
in Fig. 1. Whereby, it covers the following steps:
 Comprehend the study area; site visiting.
 Data collections and site surveys.
 Develop hydrodynamic modeling and flood
mapping.
 Generate a flood inundation map from the
integration of hydrodynamic modeling and flood
mapping output.
RESEARCH ARTICLE OPEN ACCESS

Fig. 1. Design flowchart of generation flood
inundation map.
III. COMPREHEND THE STUDY AREA;
SITE VISITING
Generally, a site visit and ground truthing is
conducted are to be familiar, identify, and investigate
the flood-prone area and flood-affected areas.
Collected data such as maps, reports and previous
studies are compared with those corresponding
during the site visit. Furthermore, consultation,
interviews and discussion on matters related to
relevant authorities, flood victims and local people
could help to understand the study area.
Inspections on floodplain physical
characteristic, existing flood condition, flow behavior
of pre and post flooding events are paramount and a
must have data to be collected during site visits.
Validation and calibration data are obtained from the
historical flood event. Flood-affected area and flood-
prone areas ought to visit with reference to
geographical data.
IV. DATA COLLECTIONS AND SITE
SURVEYS
Appropriate and comprehensive data
collection are significant to the effectiveness of the
flood inundation map. Therefore, data are collected
and obtained either from survey works or secondary
sources. Data collection may be divided into
categories:
i) Topography, digital elevation models (DEM),
and site survey
Appropriate selection of horizontal and
vertical accuracy of the DEM has significant impact
on the reliability and accuracy of the produced maps
[6]. Furthermore, to develop a hydrodynamic model
and flood map, river survey is paramount in order to
develop reliable model.
Fig. 2 is the illustration of BatuPahat District land use
map (DID, 2013).
ii) Historical data
During validation and calibration processes,
historical data are the most important data to be
collected. This is to ensure the model accuracy to
simulate future flood event. Data such as the
following are to be taken in:
 Historical flood event report
 Flood maps on related areas
 Newspaper reports or article relating
previous flood event at the selected area
 Rainfall data from several stations
 Water level record in the selected area
 Stream flow and evaporation record
Fig. 3(a) and Fig. 3 (b)illustrates land use planning of
BatuPahat district for 2002 and 2020 (DID, 2013).
Fig. 2.Flood areas during the January 2007 flood
eventintheBatuPahat district area, Johor.
(DID, 2013)
INTEGRATED HYDRODYNAMIC MODEL –
FLOOD MAPPING
Ground
survey,coordinates
Location,
Land use map data,
Topographical data,
Meteorological data,
Hydrological data
Flood Mapping
Hydrodynamic
Model
Catchment and river Flood simulation
FLOOD INUNDATION MAP BY
COMBINATION OF HYDRODYNAMIC
MODEL AND FLOOD MAPPING APPROACH

Fig. 3(a). Land Use Plan of BatuPahat District for
year 2002. (Source: DrafRancanganTempatanDan
Daerah 2002-2020)
Fig. 3(b). Land Use Plan 2020 for the river basin in
BatuPahat District. (DID, 2013)
Fig. 4.BatuPahat River Basin shows the Subdivided
Basins and location of Hydrological Stations. (DID,
2013)
iii) Land use data
In developing the HD model, land use data
are needed in order to analyze Runoff Mode of the
model. The followings are related land use data can
be obtained from subjecting authorities:
 Soil map (reconnaissance map and land use
map) – Department of Agriculture
 Value added map (hydrologic soil map, soil
classification map) – Department of
Agriculture
 Land use map (structural plan and local plan) –
Department of Urban and Rural Planning
Fig. 4 shows subdivided basins of the BatuPahat
River and the location of hydrological station.
V. HYDRODYNAMIC MODELING AND
FLOOD MAPPING
A. Hydrodynamic modeling
Hydrodynamic is a study of liquid motion
and specifically, water. The tool which describes or
represents in some way the motion of water is called
hydrodynamic modelling. Before the advent widely
available computer systems, a hydrodynamic model
could in fact be the physical model built to scale.
However, virtually all hydrodynamic models in use
today are computational numerical models.
One-dimensional (1D) model is the
traditional approach to simulate flow in river
channels. 1D modelis often used to mathematically

represent flow routing along a river reach [2]. One-
dimensional (1D) model is unable to accommodate
the true physical and hydrodynamic conditions that
are critical to understand different river processes [3].
In additional, 1D model has few limitations such as
inability to represent detailed bathymetry that affect
river process. Furthermore, the 1D model unable to
simulate hydrodynamic conditions those are prevalent
during large scale extreme events such as river
flooding and glacial out-burst floods. In fact, this 1D
model also unable to represent and simulate complex
river systems, for example anastomosing river.
However, some researchers have the opposite opinion.
Basically, in most 1D hydrodynamic models
are based on 1D unsteady state gradually varied flow
equations, this basic formulais the St. Venant
equations. As in (1) shows the mass conversion or
continuity equation, whilst (2) is the momentum
conversion or dynamic equation. Both equations are
applicable for 1D hydrodynamic modeling.
𝛿𝑄
𝛿𝑥
+
𝛿𝐴
𝛿𝑡
= 𝑐 (1)
𝛿𝑄
𝛿𝑡
+
𝛿
𝛿𝑥
𝛽 𝑄2
𝐴
+ 𝑔𝐴
𝛿ℎ
𝛿𝑥
− 𝑆0 + 𝑔
𝐴𝑄 𝑄
𝐾2 = 0 (2)
Where:
Q(x,t) = discharge (m3
/s)
t = time (s)
x = streamwise direction (m)
c = lateral inflow per unit length of flow
A(x,t) = cross-sectional area (m2
)
g = gravitational acceleration (m/s2
)
h = water level (m)
S0 = bed slope (m/m)
K = conveyance (m3
/s)
 = Boussinesq coefficient
𝛿𝑄
𝛿𝑡
is the local acceleration term.
𝛿
𝛿𝑥
𝛽𝑄2
𝐴
is convective term responsible for non
− linearity of equation .
𝑔𝐴
𝛿ℎ
𝛿𝑥
− 𝑆0 is pressure term due to change
in depth over reach − if 𝑆0 is neglected then
𝑑ℎ
𝑑𝑥
approximates thefriction slope based on
the change in water level.
𝑔
𝐴𝑄 𝑄
𝐾2
is source gravityterm causes water to flow.
Fig. 5, Fig. 6, and Fig. 7 shows example hydrograph
generation, analysis process and the result in 1D
hydrodynamic model.
Fig. 5.Example of hydrograph generation of
Sembrong River catchment area using Xpswmm tool.
Fig. 6.Example of running analysis in Xpswmm for
Sembrong River, Johor.
Fig. 7.Example of analysis result in 1D
hydrodynamic model of Sembrong River, Johor.
Use the same principle as 1D hydrodynamic
model mass conversion/continuity equation, 2D
shallow water equation was introduced as follows:
𝛿ℎ
𝛿𝑡
+
𝛿 𝑢ℎ
𝛿𝑥
+
𝛿 𝑣ℎ
𝛿𝑦
= 0 (3)
According to (3), the y axis orthogonal to the x
axis, and its flow velocity v (m/s) associated.

B. Flood mapping
To describe flood patterns, the most proper
approach is by developing flood mapping. As in [1],
flood map can be categorized as followings:
 Flood danger map – shows the spatial
distribution of the flood danger without
information about the exceedence probability.
 Flood hazard maps – shows the spatial
distribution of the flood hazard, i.e. information
on flood intensity and probability of occurrence
of single or several flood scenarios.
 Flood vulnerability map – shows the spatial
distribution of the flood vulnerability, i.e.
information about the exposure and/or the
susceptibility of flood-prone elements
(population, built environment, natural
environment).
 Flood damage risk map – shows the spatial
distribution of the flood damage risk, i.e. the
expected damage for single or several events
with a certain acceptance probability.
Developing a 3D map is time consuming,
challenging and of course highly cost. A set of detail
fieldwork dataset consist of Northing Easting
magnitude and elevation is needed. Field survey has
to be conducted in order to obtain the fieldwork
dataset. In creating a 3D flood map, northing easting
magnitudes are presented as x-axis and y-axis, and z
is presenting elevation. Z value then connected along
the lines of constants X and Y to create wireframes
right after contour lines are produced. Digital
Elevation Model (DEM) has to be setup for
overlapping process in order to create a 3D map. For
an impressive flood map, kriging gridding method can
be used as interpolation techniques [4].
Fig. 8 below shows the dataset of XYZ, Fig. 9 till Fig.
12 shows examples of the contour map, wireframes,
2D and 3D maps for a Sembrong River catchment
area.
Fig. 8. Example of a data set consists of a northing
easting magnitude and elevation.
Fig. 9. Example of contour lines produced for
Sembrong River, Johor.
Fig. 10. Example of wireframe produced for
Sembrong River catchment area.
Fig. 11. Example of 3D map produced for Sembrong
River catchment area.

Fig. 12. Examples of 3D and 2D maps indicate water
movement into Sembrong River.
VI. FLOOD INUNDATION MAP –
INTEGRATION OF HYDRODYNAMIC
MODEL AND FLOOD MAPPING
APPROACH
A flood inundation model is developed with
integration of hydrodynamic model and flood
mapping approach. The results of the flood simulation
of hydrodynamic model will be visualized through the
development of flood map. A flood inundation model
for a certain historical flood event will be constructed
for analysis to produce an inundation map. With flood
mapping approach, catchment and river mapping will
be produced, and flood simulation results will be
obtained from developinga hydrodynamic model. The
results of flood mapping and hydrodynamic model
will be combined through semi-automated process
where the topography will subtract from the water
surface to get the inundation extent.
Before finalizing the flood inundation model,
validation and calibration are a crucial step to be done
in order to minimize the discrepancies between the
developed model and the ancient river condition.
Fig. 13 below shows the example of flood
inundation model for Kota Tinggi River for January
12th, 2007 event.
Fig. 13.Example of flood inundation model for Kota
Tinggi River.
VII. CONCLUSION AND
RECOMMENDATIONS
The flood inundation model could be very
useful and valuable tools in flood management of
river basins in Malaysia. It may be used as a tool for
rivers development planning, flood mitigation
measures, addressing public awareness, and flood
evacuation planning.
As a flood inundation model would be very
useful and helpful for local authorities in flood
management, however to obtain the information
needed to develop the model is difficult and
complicated. Therefore, it is recommended that flood
information, data needed to develop the model and
developed model are compiled in web-based system.
By this way, the information can easily retrieve and
disseminate either by public or professionals.
ACKNOWLEDGEMENT
The author/authors would like to express
gratitude to the Ministry of Higher Education
Malaysia, Department of Irrigation and Drainage
Malaysia, Department of Town and Country Planning
Peninsular Malaysia, and University Tun Hussein
Onn Malaysia for the support in preparing this paper.
REFERENCES
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[2] Paz, A. R., Bravo, J. M., Allasia, D., and
Tucci, C. E. M., (2009). Large-Scale
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[3] Merwade, V., Cook, A., and Coonrod, J.,
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[4] Adib, M. R. M., Junaidah, A., Wardah, T.,
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[5] Bates, P. D. and De Roo, A. P. J., (2000). A
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