National Center for Computational Hydroscience and Engineering
CCHE2D-COAST FOR FORECASTING, PLANNING, AND INVESTIGATING COASTAL
DISASTERS DUE TO FLOODING AND INUNDATION INDUCED BY TROPICAL CYCLONES
WHITE PAPER, June, 2013
Yan Ding, Ph.D. Dr. Eng.
Research Associate Professor, National Center for Computational Hydroscience and Engineering,
The University of Mississippi, Brevard Hall 335, University, MS 38677-1848. Phone: +1 (662)
915-8969, Email: ding@ncche.olemiss.edu
0
School of Engineering,
The University of Mississippi
Summary
This white paper proposes an integrated riverine/estuarine/coastal/ocean process modeling
system, CCHE2D-Coast, for forecasting, planning, and investigating coastal disasters due to flooding and
inundation caused by tropical cyclones (tropical storms and hurricanes). CCHE2D-Coast, which is
developed in the NCCHE in the University of Mississippi, consists of four major modules (submodels): (1)
wave action model for computing deformation and transformation of multidirectional/irregular waves
from deepwater in oceans to shallow water at coasts and estuaries, (2) tropical cyclone parametric wind
model with landfall effect for simulating atmospheric pressure and wind fields along storm tracks, (3)
flow (current) model for simulating hydrodynamic processes including astronomical tides, storm surges,
wave setup, river inflows, nearshore currents, and the Coriolis effects, and (4) sediment transport model
for computing sediment transport rates and morphological changes in river beds, coastal zones, and
estuaries.
CCHE2D-Coast has been extensively verified and validated by simulating riverine, coastal,
estuarine, and ocean processes driven by tides, waves, river flows, and sediment transport. It has been
successfully applied to simulate a variety of coupled coastal hydrodynamic and morphodynamic
processes such as coastal flooding and inundations, beach erosion, coastal inlet channel sediment
refilling, local scour around structures, and sand bar breaching due to extreme hurricane/storm waves,
surges, and river floods. It has been demonstrated that this model is effective and efficient for managing
and planning coastal disasters due to severe flooding and inundation, and for designing and planning
coastal infrastructures such as levees, dikes, breakwaters, waterways, and harbors, by considering both
hydrodynamic and morphodynamic impacts due to disastrous storm events (hurricanes and typhoons).
It also has been used to forecast storm surges and waves during tropical cyclone seasons such as
Hurricane Isaac (2012) in the Gulf of Mexico and Hurricane Sandy (2012) in the U.S. East Coast. It has
been used to assess both hydrological and morphological impacts of sea level rise and climate change
under tropical cyclonic weather conditions on river mouths, shorelines, and coastal communities. This
model has been also used for post-disaster investigation in the Mississippi Gulf coast by investigating the
impacts of the new coastal protection systems of New Orleans on the flood levels along the Mississippi
coastline and the inland areas. Moreover, an ad-hoc GIS-application tool has been developed by the
NCCHE to connect CCHE2D-Coast simulation results with FEMA’s risk assessment tool (HAZUS-MH) to
provide a quick assessment tool to map risks of hazards and damage of properties due to storm surges
and waves. In summary, CCHE2D-Coast is a comprehensive simulation-prediction-analysis tool for
forecasting, planning, and investigating coastal disasters induced by tropical cyclones.
It is important to note that all the modules share one grid system for simulating these
hydrodynamic and morphodynamic processes in sequence. Instead of using the so-called model steering
operation adopted in other storm-surge models, CCHE2D-Coast does not need to switch executable
codes of the modules. As a result, this model eliminates possible errors and loss of information due to
interpolation and extrapolation of the results between different grid systems for different process
models. The mesh of CCHE2D-Coast is non-orthogonal, which allows general structural quadrilateral
grids. Thus, a structural computational grid with spatially-varying mesh resolutions can be created to
model irregular coastlines in a flexible way, and enables to focus on different regions of interest in
coastal zones, estuaries, and inland watersheds with complex geometries. Computationally, implicit
numerical schemes for solving all the governing equations of waves, currents, and morphological
changes make this integrated model efficient and capable of running simulations in a standard laptop
computer with a relatively short computational time.
Finally, this white paper proposes further developments for CCHE2D-Coast to enhance its realtime prediction capability as a potential operational system for coastal disaster forecasting and
1
management. Further speed-up of simulations will be done by parallelizing all the process modules to
provide forecasting results within an hour on a standard multicore PC. This operational system will be
able to perform highly accurate predictive simulations by automatically assimilating observation data
such as storm advisory paths, water elevations at tidal gauges, and wave heights at buoys. The sediment
transport models will be enhanced to compute sediment transport in sandy coasts and muddy waters in
which cohesive sediments are dominant in wetlands and tidal marshes in the northern Gulf coasts. All
the simulation results will be readily mapped by means of FEMA’s risk assessment tools (e.g. HAZUS) and
the NCCHE’s GIS application platform.
Contents
Summary ....................................................................................................................................................... 1
1. Introduction of CCHE2D-Coast .................................................................................................................. 3
2. CCHE2D-Coast’s Capabilities for Forecasting, Planning, and Investigating Coastal Disasters Induced by
Flooding and Inundation ............................................................................................................................... 5
2.1. Preparedness and Planning................................................................................................................ 6
2.2. Forecasting, Emergency Management, and Operational Modeling .................................................. 9
2.3. Hindcasting for Forensic Investigation............................................................................................. 11
2.4. Mapping of flood risks based on GIS and flood risk assessment tool (CCHE2D + HAZUS) .............. 13
3. Further development for enhancing the model’s capabilities................................................................ 16
References .................................................................................................................................................. 17
2
1. Introduction of CCHE2D-Coast
CCHE2D-Coast is an integrated riverine/coastal/estuarine/ocean processes modeling system,
which is developed in the National Center for Computational Hydroscience and Engineering (NCCHE) in
the University of Mississippi. It is applicable for simulating multi-scale hydrodynamics and
morphodynamics of free-surface water flows such as river flows, tidal currents, waves, storm surges
induced by tropical cyclonic wind, sediment transport, and morphological changes over large-scale
coastal regions. This modularized application software is developed by using the state-of-art numerical
simulation techniques and innovative physical knowledge in river, coastal, and ocean engineering. The
model has been validated and verified by using laboratory-scale experimental data and regional-scale
field data. It has been applied to solve engineering problems for flooding and inundation management,
erosion protection, and infrastructure planning and design in coasts and estuaries. The integrated model
is embodied into a user-friendly interface, CCHE2D-GUI, which supports this integrated model for
generating computational grids, monitoring computational progress during computations, and
visualizing numerical results during and after simulations. CCHE2D-Coast is able to simulate large-scale
and long-term problems on a standard PC. The low cost and accurate simulations make this tool
specifically attractive to engineers and researchers in the areas.
CCHE2D-Coast has integrated systematically four major submodels for simulating deformations
and transformations of irregular/multidirectional waves, tropical cyclonic barometric pressure and wind
fields along storm tracks, tidal and wave-induced currents, and coastal morphological changes (Figure 1).
For computing irregular waves, a multi-directional spectral wave action equation is adopted in the wave
spectral module. The following wave deformation/transformation processes are included in the
CCHE2D-Coast wave model:
 Refraction
 Diffraction
 Shoaling effect
 Wave breaking
 Wave transmission through coastal structures
 Bottom friction
 Wave-current interaction
 Vegetation attenuation effect
 Wind-induced waves
 Whitecapping
Hydrodynamics
Wind Module
(Storm track, wind, air
pressure)
Tidal Module
(Boundary conditions, tidal
constituents)
Morphodynamics
Wave Model
Current Model
(Refraction, Diffraction,
wind energy input,
Breaking,
whitecapping,wave
transmission, etc.)
(Wind shear stress,
Radiation Stress, Surface
Roller Effect, Colioris Force
Bed Friction, Turbulence)
Sediment
Transport Model
Morphological
Change Model
(Sediment flux due to
wave and current)
(shoreline evolutions)
Figure 1. Flow chart of the CCHE2D-Coast model
CCHE2D-Coast provides two options for modeling wave actions: a half-plane wave model and a
full-plane wave model (Ding et al. 2012b, 2013b). The former is to compute wave fields only from the
upwinding direction to the downwind direction, for example, to simulate deformation and
3
transformation processes of swelling waves from deepwater to shallow waters at shore. The latter is the
simulation option by which the computations of wave fields are performed by scanning the domain back
and forth in wind directions. The full-plane wave simulation can be used for computing waves induced
by cyclonic wind fields.
In this model, a nonlinear parametric hurricane cyclonic wind module is integrated to model
cyclonic barometric pressure and wind fields along storm tracks by considering the decay effect of
landfall and the earth surface resistance (Ding et al. 2013c). By simulating historical hurricanes in the
northern Gulf Coast, a database for determining the parameter values for decay and land surface
resistance has been established (Ding 2012). By implementing into CCHE2D-Coast, this integrated model
has been validated by simulating wind and storm surges in Hurricane Gustav (2008), and used for
forecasting wind fields and storm surges induced by Hurricane Isaac (2012) and Sandy (2012).
For the hydrodynamic simulations in coasts and estuaries, the 2-D depth- and shortwaveaveraged shallow water equations are employed to simulate the currents driven by wave radiation
stresses, tides, storm surges, river inflows, the Coriolis force, and turbulence in surf zones, tidal zones,
and ocean waters. This hydrodynamic model provides users with two options to calculate wave
radiation stresses: one is the traditional wave stress formulations by means of sinusoidal wave
assumption by the linear small-amplitude wave theory; another is the improved radiation stresses
formulae derived from the non-sinusoidal wave assumption (Svendsen 1984, Ding et al. 2006) which
enables to take into account the 3-D features of the vertical current structures (e.g. the surface rollers or
the undertow currents) in the surf zone. According to Svendsen et al. (2003ab) and Ding and Wang
(2008a), the non-sinusoidal wave radiation stresses can produce more accurate nearshore currents in
surf zone than the former one. In the morphodynamic submodel, empirical sediment transport models
are used to calculate the sediment transport rates contributed from bed materials and suspended
sediment under the conditions of combined waves and currents. To compute morphodynamic processes
in coasts and estuaries, a unified sediment transport model (Ding and Wang 2008a) is used to calculate
the sediment flux from upstream rivers to estuaries and coasts to consider seamlessly the sediment
transport from a non-wave environment at river, to a wave-current interaction area at estuary and a
wave-dominant coastal zone. The morphological changes are computed on the basis of the mass
balance of sediments in which wetting and drying process is properly modeled to handle tidal variations
and bed changes.
This integrated model for simulation of coastal and estuarine morphodynamic processes has
been built in a software package called CCHE2D, which is an integrated riverine process simulation
model to analyze 2-D shallow water flows, sediment transport, and water quality, with natural flow
boundary conditions (CCHE2D 2011). Similar to the CCHE2D hydrodynamic model, the governing
equations of three submodels (modules) in CCHE2D-Coast, i.e., the wave-action equation, the shallow
water equations, and the morphological changes equation, were discretized in a non-orthogonal grid
system (Zhang and Jia 2005). Because non-orthogonal meshes have less restrictions for grid shapes than
curvilinear grids (orthogonal grids), CCHE2D-Coast has more flexibility to simulate physical variables in
complex coastal zones with irregular coastlines. In the process of executing simulations, all the
submodels are working with the same computational grid. Therefore, the wave and flow models are
running on the same computational cores, passing information between submodels through local
memory/cache, and thus they simulate the propagation of waves from deep water to shallow water in
nearshore without any interpolations between the wave and the flow fields. Unlike the so-called model
steering operation used in other storm-surge models, CCHE2D-Coast does not need to switch executable
codes of the submodels during computations. As a result, CCHE2D-Coast avoids possible errors and loss
of information due to interpolation and extrapolation of the results between different grid systems so
that simulations by this integrated model are computationally efficient and accurate.
4
A validated algorithm in the CCHE2D for the treatment of wetting and drying in the
computational area was directly used for predicting tidal flat variations and coastal flooding and
inundations. An implicit time-marching algorithm proposed by Jia et al. (2002) was used to compute the
tidal and wave-induced currents. The simulation time step size, therefore, is not restricted by the CFL
(Courant–Friedrichs–Lewy) condition which the explicit schemes have to follow in the hydrodynamic
computation. A time step as long as several minutes can be used for computing most large-scale stormsurges driven by tropical cyclones. For a typical one-week storm simulation, CCHE2D-Coast is able to
accomplish simulations covering a regional domain (e.g. the Gulf of Mexico or the entire U.S. East Coast)
within several CPU hours on a single core standard PC (e.g. Ding et al. 2012ab, 2013c)
As a summary, CCHE2D-Coast has the following principal features for simulating hydrodynamic
and morphodynamic processes driven by tropical cyclones:
 Deformation and transformation of multidirectional and irregular waves,
 Tidal currents and River flows,
 Coriolis force,
 Tropical cyclonic wind and atmospheric pressure
 Bottom friction,
 Storm surges and wave setup induced by cyclonic wind and wave fields
 Nearshore currents induced by short-period waves
 Sediment transport due to waves and currents,
 Coastal/estuarine morphodynamic processes
 Morphological changes around coastal structures, e.g., groins, offshore breakwaters, artificial
headlands, jetties, artificial reefs, etc.
2. CCHE2D-Coast’s Capabilities for Forecasting, Planning, and Investigating Coastal Disasters
Induced by Flooding and Inundation
For various engineering application purposes of predicting, investigating, and planning coastal
hazards such as flooding, inundations, and erosion, CCHE2D-Coast has been applied to simulate a variety
of coupled coastal hydrodynamic and morphodynamic processes such as coastal inundations, beach
erosion, coastal inlet channel sediment refilling, local scour around structures, and sand bar breaching
due to extreme hurricane/storm waves, surges, and river floods (Ding et al. 2006; Ding and Wang
2008ab; Kuiry et al. 2010, Ding et al. 2012abc, Ding et al. 2013abc). It also has been used to forecast
storm surges and waves during tropical cyclone seasons such as Hurricane Isaac (2012) in the Gulf of
Mexico and Hurricane Sandy (2012) in the U.S. East Coast (Ding et al. 2013c), and to assess the impacts
of storm surges under sea level rise scenarios due to the future climate change (Ding et al. 2013b).
Figure 2 shows a flow chart for using the model to acquire hydrological, geomorphic, infrastructural, and
meteorological data, to execute the model, and to analyze simulation results by mapping flooding and
inundation. A few application examples of CCHE2D-Coast for planning, forecasting, and investigating
coastal hazards are given as follows:
5
Simulation and Prediction
(Scenario Studies, Real-time Prediction, Storm Water Management and Planning)
Bathymetric Data
(Beaches, Barrier
Islands, Inlets,
Marshes, Rivers, etc.)
Structure Data
(Levees, Jetties,
Waterway, etc.))
Meteorological
(Wave, Wind, Air
Pressure, Hurricane
Track) Data
Hydrological (Tides,
River Discharge) Data
Sediment Properties
and Flux Data
Observation Data
Hurricane
Wind Model
Hazard Maps
Emergency Planning
Forensic Investigation
Tide Model
Flooding/Inundation Maps
Wave Model
Flow Model
Shoreline Erosion
Protection, Local Scour,
Barrier Island Breaching
Sediment
Transport
Model
Morphological
Change Model
Cost-effective Structure
Design
Integrated Coastal
Process Model
Coastal Hazard Planning and
Management
Figure 2 Integrated modeling system based on CCHE2D-Coast for planning and management of flood and
inundation
2.1. Preparedness and Planning
Traditionally, standard engineering design manuals have provided engineers with a year-return
flood discharge and an extreme wave height in coasts as design criteria for managing flood and erosion
(e.g. Coastal Engineering Manual 2002). However, these design conditions based on statistical values
may overlook real dynamic and nonlinear impacts of physical forcings from rivers and oceans. Therefore,
it becomes more important to use representative physical events (processes) (e.g. an entire flooding
hydrograph or a whole hurricane season) as design criteria to represent the magnitude of the physical
forcings and the historical processes of natural events in flood and tropical storms. In terms of
representative events, integrated process models are able to predict long-term responses of coastal
design structures including hard structures such as levees and breakwaters, and soft engineering
approaches such as beach nourishments and adaptive flood controls.
By adopting the design conditions of representative events based on combined tropical cyclones
and river flood flows, CCHE2D-Coast has been applied for evaluation of engineering designs of coastal
structures and dredging for flood prevention, erosion, and sedimentation in an estuary in Taiwan (Ding
and Wang 2008b, Ding et al. 2013a). Prior to applying the model for design of the estuary, this model
was carefully validated by simulating long-term morphological changes under the historical hydrological
conditions (including typhoon seasons and monsoons) in the site (hindcasting morphodynamic
processes from 2004-2006) (Ding et al. 2008b). To design of coastal installations, the effects of episodic
6
events (historical typhoons and a hypothetical 100-year flood from upstream rivers) have been
evaluated in both short- and long-term simulations. The results of the predicted flow fields and
morphological changes are physical reasonable, especially the spatial and temporal trend of variations is
realistic. As an example, Figure 3 (a) shows computed significant wave heights (color contours) and
mean wave directions (arrows) in the estuary at the time when a typhoon was passing the project site;
and Figure 3 (b) presents the simulated flood current and water elevations in the estuary at the peak
flood driven by combined forcings of waves, tides, river floods, and sediment transport, in which the
breaching of the rivermouth bar and the overbank flooding were predicted. The water elevations at the
peak flood shown in Figure 3 (b) directly captured the maximum flooding/inundation areas in the
estuary and its adjacent coasts. The computed morphological changes by CCHE2D-Coast shown in Figure
4 quantified the coastal erosions on the river mouth bar, inside the estuary, and offshore, as well as the
deposition in the tidal river reach upstream, and bar development offshore.
The validated CCHE2D-Coast model was then applied to search for the best coastal/estuarine
plan from a number of engineering conceptual plans which were proposed to manage flood flows and
sedimentations in the area. Figure 5 presents six engineering plans, which include (1) installation of a
7.0-m high dike to protect the south bank of the river in Cases 2, 3, 4, and 7; (2) dredge of a channel in
Cases 3, 4, and 6; (3) removal of an Island in the center of the estuary in Cases 6 and 7; and (4)
installation of a jetty to separate waters in the river mouth in Case 5. In order to investigate the
performance of these engineering plans, simulations of hydrodynamic and morphodynamic responses to
a hypothetical extreme typhoon event and a monsoon event were performed. Based on the large
amount of results for flood water stages and long-term morphological changes, the best plan for
minimizing the flood water elevations and morphological changes was found (Ding et al. 2013a).
(a) Computed wave heights and mean directions
7
(b) Computed currents and Water Elevations at the peak flood
Figure 3. Simulations of storm waves and flood flows in a Taiwan estuary driven by combined forcings, i.e.
storm waves, river floods, tides, and sediment transport
Figure 4. Computed morphological changes after a storm in a Taiwan estuary driven by combined forcings,
i.e. storm waves, river floods, tides, and sediment transport (Red=Deposition, Blue=Erosion)
8
Case 4
Case3
Case 2
Dredge
Dike
-W-d¸}³
• Dike (+7.0-m high)
• Land Reclamation
Dike
Dredge
Dike
• Dike (+7.0-m high)
• Dredge of Channel
• Land Reclamation
• Dike (+7.0-m high)
• Dredge of Channel
Case 7
Case 6
Case 5
Remove Island
Remove Island
Dredge
Jetty
Dike
苦苓腳堤
• Jetty to separate the two rivers
右股河道疏浚
苦苓腳堤防
Dike
• Dike (+7.0-m high)
• Remove Beilaio Island
• Dredge of Channel
• Land Reclamation
• Dike (+7.0-m high)
• Remove Beiliao Island
Figure 5 Engineering Plans for Flood and Erosion Protection in Touchien Estuary
2.2. Forecasting, Emergency Management, and Operational Modeling
Because of its excellent simulation performance, CCHE2D-Coast is able to predict storm surges
over a regional domain driven by tropical cyclones in the Gulf of Mexico and the U.S. Atlantic Ocean. In
the case of forecasting hurricane wind fields and storm surges during Hurricane Isaac (2012) (see Figure
6), all the predictions were performed on a PC with a 2.70 GHz Intel Core i7. By using a total nodal points
of 2,288,064 covering the northern Gulf coast including the Louisiana, Mississippi, and Alabama coasts,
one-day simulation under interaction of wave and current takes 4.5 hours on a single CPU. Thus, the
simulation of storm surge over this regional computational grid runs 5.3 times faster than real time by
using only one CPU (Ding et al. 2013c). It is important to underline that CCHE2D and CCHE2D-Coast can
be run on a PC, whereas most of the standard used models (such as ADCIRC) require costly use of
supercomputers to achieve a similar performance.
A parametric model developed by Ding et al. (2013c) for predicting hurricane wind field
traveling inland after making a landfall was used for the forecasting. The use of parametric models
greatly facilitates the efficiency of CCH2D numerical model without sacrificing accuracy.
During the period of Isaac, CCHE2D-Coast was started to run the forecasting cases of tropical
storm wind and storm surges based on the NHC (National Hurricane Center) advisories (i.e. track, central
pressure, hurricane size, etc.). These advisories are #27 at 2100 UTC, Aug. 27, #29a at 1200 UTC Aug. 28,
#30a at 1800 UTC Aug. 28, and #39 at 2100 UTC, Aug. 30. Data for the wind field, track, and hurricane
landfall decay were updated with the latest updated observations upon each new simulation, with the
Advisory #39 run serving as a best-track simulation. By utilizing the most effective formulations and
modeling schemes devised in this study, highly accurate forecasts of wind speeds and water elevations
9
at data stations were achieved (Figure 7). Though forecast accuracy increased expectedly with additional
advisories, culminating in the best-track simulation based on Adv. #39, calculated maximum intensities
readily matched observed values even for the initial simulation at Adv. #27, nearly two days before
landfall.
Figure 6. Left: Best track positions for Hurricane Isaac, 26 August – 1 September 2012 (Berg 2013). Right:
Predicted maximum water elevations during Isaac for the Advisory #39 forecast
Water Elevations at St. 26 (Shell Beach, LA)
Water Elevations at St. 27 (Bay Waveland Yacht Club, MS)
5
Observation
Advisory #27
Advisory #29a
Advisory #30a
Advisory #39
4
Water Elevation above NAVD88 (m)
Water Elevation above NAVD88 (m)
5
3
2
1
0
08/25 00:00
08/27 00:00
08/29 00:00
08/31 00:00
09/02 00:00
Observation
Advisory #27
Advisory #29a
Advisory #30a
Advisory #39
4
3
2
1
0
08/25 00:00
08/27 00:00
08/29 00:00
08/31 00:00
09/02 00:00
Figure 7. Predicted water elevations at two sample stations for NHC’s advisory tracks (#27, 29a, 30a, and 39)
The team in NCCHE has also performed a preliminary simulation model test of Hurricane Sandy
(2012) using CCHE2D-Coast, based on a request from the DHS S&T Program Coordinator in order to
demonstrate the capabilities of the underlying numerical model to higher levels in the DHS
administration. Hurricane Sandy was the deadliest and most destructive tropical cyclone of the 2012
Atlantic hurricane season, as well as the second-costliest hurricane in United States history (Blake et al.
2013).
Figure 8 shows the results of the computed water elevations in Montauk, NY, and Sandy Hook,
NJ, and compares with the observation data obtained from the NOAA tide gauges. Similar patterns and
matches were derived for a number of coastal locations along the NJ Coast and other areas affected by
Sandy. As can be seen in this figures, the model results show an exceptionally good level of match with
real recorded data at all locations studied along the East Coast.
10
Figure 8. Comparisons of Water Elevations at Montauk, NY and Sandy Hook, NJ during the period of
Hurricane Sandy (2012)
The simulations were performed using the CCHE2D software, which comes with its own userfriendly and efficient mesh generator. As mentioned above, it is a two dimensional finite element model
that can simulate not only hydrodynamics for inland fluvial flows and storm surges during hurricanes by
taking into account wave effect, but also sediment transport, fluvial and/or coastal morphodynamics,
contaminant transport and fate and water quality.
In Ding et al. (2013b), the NCCHE team has assessed the impact of sea-level rise and hazardous
storms on coasts and estuaries using this integrated processes model. Unlike most other studies of sealevel rise which do not consider sediment transport and coastal morphodynamics, an integrated
approach was adopted which takes into account these important processes as well. The paper describes
the coastal sediment transport and morphodynamics capabilities offered by the CCHE2D-COAST model.
Coastal morphodynamics can be an important issue during hurricanes, as the events during Hurricane
Sandy, and many others, have shown. Many other models use a fixed bed concept, which assumes that
the coastal morphology does not change. As now known and studied in (Ding et al. 2013b), island
barriers, tidal inlets, beaches may undergo severe changes, which in turn may affect storm surge and
flooding depths.
2.3. Hindcasting for Forensic Investigation
CCHE2D-Coast has been extensively used to handcast coastal hazards such as flood,
sedimentation, shoreline erosion, and local scouring induced by river floods and tropical cyclones. The
purposes of hindcasting coastal hazardous events are for model validations and forensic investigations.
Each module of this integrated coastal process model has been validated by simulating wave
deformation and transformation processes such as refraction, diffraction, breaking, and wave-current
interaction in laboratory-scale experiments and field cases (e.g. Ding et al. 2006, Ding and Wang 2008a,
Ding and Wang 2011). Morphodynamic processes in the model have been also carefully validated by
reproducing morphological changes around coastal structures (Ding et al. 2006) and scouring in river
mouth bars (Ding et al. 2008b, Ding et al. 2013b). All these rigorous model validation efforts make all the
physical process modules capable of producing highly accurate numerical results of coastal hazards for
reliable and cost-effective management and decision making.
11
For example, funded by the Mississippi Department of Marine Resources, the NCCHE scientists
have hindcasted Hurricane Gustav (2008) to investigate the flooding and inundation in the Pearl River
estuary in Mississippi (Ding et al. 2012a). By using CCHE2D-Coast, they have simulated storm surges and
waves driven by hurricane wind, tides, waves, and river inflows in a large-scale domain covering the
Mississippi and Louisiana Gulf Coasts. By using existing bathymetric data in an ADCIRC mesh (Bunya et al.
2010) and USGS 10-meter resolution DEM topographic data, a high-resolution mesh is generated to
represent structures, roads, rivers, barrier islands, and lakes (see Figure 9). For study of flooding and
inundation by hurricanes in the inland areas of the Mississippi Gulf Coast, the Pearl River and its
floodplain are included in the mesh with a detailed river course (Figure 10). The configurations of
coastal infrastructures such as levees and dikes in Louisiana by 2007 and 2011 have been considered in
the simulations. Computed maximum storm surges without the Pearl River are compared with those
with the river inflow. Differences in storm surges indicate that the inclusion of the river inflow is
imperative in order to obtain accurate predictions on flood and inundation due to storm surges in the
Mississippi Coast community (Figure 11). And the difference in surge heights due to the configuration
of coastal defense structures has been found in the east coast of Louisiana. It implies that this model,
with spatially-varying mesh resolution, not only can reproduce the flooding and inundation in a largescale coastal region, but also is capable of focusing on the regions of interest, which includes various
spatial scale processes in inland areas with complex geometries.
(a)
(b)
Figure 9. (a) Computational mesh consisting of 2,288,064 nodes which covers the northern Gulf coast for
studying storm surges and waves by hurricanes; (b) Enlarged view showing the Lake Pontchartrain and the
Pearl River.
12
(a)
(b)
Figure 10. (a) Enlarged view showing the high-resolution topography in the Pearl River. (b) Enlarged view
showing the mesh in the Pearl River.
(a) No river flood from inland
(b) with river flood from the Pearl River
Figure 11. Close-up view of maximum water depth at the Pearl River in Mississippi: (a) no flood from the
upstream of the Pearl River, and (b) with flood from the Pearl River ( Discharge =150.0m3/s)
2.4. Mapping of flood risks based on GIS and flood risk assessment tool (CCHE2D + HAZUS)
Several ad-hoc GIS-application tools have been developed for CCHE2D-Coast to obtain bed
roughness coefficients (i.e. Manning’s n values) based on land uses and land covers (Figure 12). The
13
maximum flood water areas obtained by the model can also be mapped by creating shape files for the
GIS-application tool (e.g. Figure 6).
n = 0.025
n = N/A
n = 0.016
n = 0.030
n = 0.030
n = 0.050
n = 0.03
n = 0.035
n = 0.025
n = 0.12
n = 0.20
Figure 12. Bed roughness coefficients (i.e. Manning’s n values) assigned based on the USGS National Land
Cover Data (NLCD) in Louisiana and Mississippi
The NCCHE scientists have developed a GIS-based interface, which is to evaluate and visualize
flood risks and damage of properties on the GIS platform by connecting CCHE2D-Coast simulation
results with the FEMA's HAZUS-MH software. By generating HAZUS compatible 2D flood depth grid for
an evaluation coastal area, this GIS-based interface can quickly produce assessment maps of flood risks.
Figure 13 (a) shows the flow chart of how the GIS-application tool couples HAZUS (Hazards-United States)
and CCHE2D-Coast.
HAZUS-HM, which is developed by FEMA, provides nationally applicable, standardized
methodologies for estimating potential wind, flood, and earthquake losses on a regional basis. HAZUS
can be used to conduct loss estimation for floods and earthquakes, and contains a preview model for
hurricane loss estimation. The multi-hazard HAZUS is intended for use by local, state, regional officials
and consultants to assist mitigation planning and emergency response and recovery preparedness. For
14
some hazards, HAZUS can also be used to prepare real-time estimates of damages during or following a
disaster (FEMA 2009).
The HAZUS Flood Model is for floodplain managers, their contractors, and others who are
responsible for protecting citizens and property from the damaging effects of flooding. It is an
integrated system for identifying and quantifying flood risks based on state-of-the-art analysis. It
provides an analytic, decision support tool to help communities make informed decisions Regarding land
use within their flood prone areas (FEMA, 2009).
By coupled with HAZUS, this integrated coastal model can (1) provides necessary data and tools
to prepare data simulate coastal flood using CCHE2D Coast, and (2) process the CCHE2D-Coast derived
flood simulation result and make it compatible for HAZUS damage analysis. During the time of
forecasting of Hurricane Isaac, this GIS-application tool was applied to evaluate potential flood risk and
damages of properties in the Mississippi Gulf coast due to storm surges by Isaac (Hossain et al. 2013).
Based on the depth grid for flood simulated by CCHE2D-Coast on August 29, 2012 for the NHC Advisory
# 29a, the total number of damaged residential houses in the coastal counties of Mississippi was
calculated by HAZUS using CCHE2D-Coast flood simulation (see Figure 13 (b)). Furthermore, the total
number of substantially damaged residential houses in the MS Gulf coast can be also obtained from the
GIS interface with HAZUS (please refer to Hossain et al. 2012 for the details).
By coupling with FEMA risk assessment tools, CCHE2D-Coast has a great potential to be a realtime operational risk assessment tool for flood emergency responders, floodplain managers, and local
government agencies to estimate physical, economic, and social impacts of disasters, and to manage
and mitigate coastal hazards.
(a)
(b)
Figure 13. (a) Coupling of CCCHE2D-Coast derived depth grid With HAZUS. (b)Total number of damaged
residential houses in the coastal counties of Mississippi by Hurricane Isaac as calculated by HAZUS using
CCHE2D-Coast flood simulation, August 29, 2012.
In summary, CCHE2D-Coast is a comprehensive simulation-prediction-analysis tool for
forecasting, planning, and investigating coastal flooding and inundation induced by tropical cyclones:
15
1. This model is capable of simulating multi-scale hydrodynamic and morphodynamic processes
such as hurricane wind, waves, storm surges, astronomical tides, river inflows, sediment
transport, and morphological changes in rivers, estuaries, coasts, and oceans.
2. CCHE2D-Coast is an effective application tool for planning and designing infrastructure in all the
water regions such as levees, dikes, breakwaters, artificial reefs, etc. to meet multiple
engineering purposes such as flood mitigation, erosion protection, and waterway maintenance.
3. Because of its excellent computational efficiency, these multi- and large-scale physical processes
in a regional scale coast can be computed by the model on a standard PC. It is attractive to use
this model for real-time or even faster-than-real-time predictions of coastal hazards caused by
tropical cyclones.
4. CCHE2D-Coast can be used to investigate various impacts of extreme flood condition due to
hurricanes in a large-scale domain, and also to be able to focus on the region of interest by
varying spatial resolution of computational grid from deepwater offshore to shoreline and
inland watershed. It makes the model capable of investigating impacts of hurricanes from ocean
waters to inland river floods.
5. By coupling with GIS-application tool and FEMA risk assessment software, this model can readily
create the flood risk maps and quickly estimate damages of properties in coastal communities. It
has a potential to be an operational tool for forecasting coastal hazards and managing
emergency and risk induced by tropical cyclones.
3. Further development for enhancing the model’s capabilities
To effectively provide solutions for managing coastal hazards induced by tropical storms, the
current integrated coastal model can be further developed by enhancing model’s computational
efficiency, automatic data acquisition, and decision making. As an ultimate goal, an integrated datadriven river/coastal/estuarine process prediction system will be built on the computational models of
different dimensions and time scales, measurement infrastructure, and regional cyberinfrastructure to
predict and analyze coastal disasters such as flood/inundation, storm/hurricane surges, storm waves,
and shoreline erosions, and further to apply to coastal flood water emergency management, hazardous
flood mapping, and erosion protection planning based on the GIS application platform (see Figure 14).
To do so, essential components requires technical advances in the following research aspects:
(1) Parallelize all the modules for computing waves, flows, and morphological changes to
significantly speed up long-term simulations of tropical cyclones. For example, by using
multicore parallel computing technique, prediction of storm surges and waves over a 72-hour
forecasting window may only take few ten minutes on a desktop computer with 16 cores;
(2) Build an automatic data acquisition system by connecting simulation/prediction models with
existing network of observation systems containing storm track information, wave gauges, tide
gauges, hydrologic stations, etc;
(3) Manage varied data sources required by the models of different dimensions and functions, e.g.
hydrologic data (water
stages, river
hydrographs, wave
properties, etc),
bathymetric/topographic data with different datum, meteorological data (wind, precipitation,
temperature, and hurricane parameters (track, central pressure, moving speed), etc);
(4) Develop an optimization algorithm to perform data-assimilation predictions by minimizing
computational errors between predicted results and observation data (e.g. water stages, wind
speed, and wave heights); This will eventually lead to develop an integrated data-driven coastal
process model, which has all the capabilities for standing as an operational
simulation/prediction modeling system;
16
(5) Enhance the sediment transport modules of CCHE2D-Coast to compute both non-cohesive
(sands) and cohesive (mud) sediment transport so that it enables to simulate a wide range of
morphodynamic processes in the northern Gulf coast waters including wetland and tidal
marshes in the Louisiana, Mississippi, and Alabama. The effect of vegetation in marshes will be
included in the models of waves, currents, and sediment transport.
(6) Integrate simulation/prediction models for computing flood flows with multiple spatial scales,
e.g. one-dimensional (1D) model for simulations of river flood flows including river basin, twodimensional (2D) model for estuarine and coastal regions, so that the integrated model system
enables to more efficiently predict flood waters from upstream river basin to coastal watershed
and estuarine regions;
(7) Enhance the existing GIS-application tool to create flood maps and to quickly assess flood risks
during the forecasting period;
(8) Develop other modules to facilitate flood water management and planning, emergency
responding, and risk assessment by coupling with other FEMA’s emergency management tools.
Gauge
Observations
Wireless
Sensors
Lidar Data
DEM Data,
etc
Computer
Graphic
Software
Hydrological
Data: Tides,
Waves, Surges,
Winds,
Hurricane
Tracks
Bathymetric/
Topographic
Data,
Sediment and
morphological
data
Visualization,
Data
Dissemination,
and User
Interface
Data Control,
Acquisition
Dynamic
Computation
(Coastal/Ocean
Models)
High
Performance
Computing
for Modeling
& Simulation
Decision
Making,
Emergency
Management,
Coastal Water
Planning
Network Connection, Network Computing, Internet
Weather Model
for Wind
Forecasting
Figure 14 A schematic diagram showing data-driven dynamic coastal model within cyberinfrastructure
References
Berg, R.(2013). Tropical Cyclone Report, Hurricane Isaac, (AL092012), 21 August – 1 September 2012,
NOAA/National Hurricane Center, 78 pp., Available at
http://www.nhc.noaa.gov/data/tcr/AL092012_Isaac.pdf
Beven II, J. L., and Kimberlain, T. B. (2009). Tropical Cyclone Report, Hurricane Gustav, 25 August–4
September 2009. NOAA/National Hurricane Center, 38 pp., Available at
http://www.nhc.noaa.gov/pdf/TCR-AL072008_Gustav.pdf.
17
Blake, Eric S., Kimberlain, Todd B., Berg, Robert J., Cangialosi, John P., and Beven II, John L. (2013).
Tropical Cyclone Report - Hurricane Sandy, National Hurricane Center, Feb 12, 2013, Available at
http://www.nhc.noaa.gov/data/tcr/AL182012_Sandy.pdf
Bunya, S., Dietrich, J. C., Westerink, J. J., Ebersole, B. A., Smith, J. M., Atkinson, J. H., Jensen, R., Resio, D.
T., Luettich, R. A., Dawson, C., Cardone, V. J., Cox, A. T., Powell, M. D., Westerink, H. J., Roberts, H. J.
(2010). A High-Resolution Coupled Riverine Flow, Tide, Wind, Wind Wave, and Storm Surge Model
for Southern Louisiana and Mississippi. Part I: Model Development and Validation, Monthly
Weather Review, 138(2), pp345-377.
CCHE2D (2011). http://www.ncche.olemiss.edu/software/cche2d, Accessed on Feb. 17, 2011.
Coastal Engineering Manual (2002). Coastal Engineering Manual, Part II: Coastal Hydrodynamics, US
Army Corps of Engineers, ERDC, Report Number: EM 1110-2-1100.
(http://140.194.76.129/publications/eng-manuals/em1110-2-1100/PartII/PartII.htm )
Ding, Yan, Wang, Sam S. Y., and Jia, Yafei (2006), Development and validation of a quasi threedimensional coastal area morphological model, J. Waterway, Port, Coastal, and Ocean Engineering,
ASCE, Vol.132, No.6, pp. 462-476.
Ding, Yan, and Wang, Sam S. Y. (2008a). Development and application of coastal and estuarine
morphological process modeling system, Journal of Coastal Research, Special Issue No. 52, pp127140.
Ding, Yan and Wang, Sam S. Y. (2008b). Numerical simulations of coastal flood and morphological
change due to hazardous hydrological conditions at coast and estuary, In: Solutions to Coastal
Disasters 2008, Ed. By Louise Wallendorf et al., ASCE, Proceeding of Solutions to Coastal Disasters
2008 Conference, April 13-16, 2008, Oahu, Hawaii, pp. 349-360 (ISBN: 978-0-7844-0968-8).
Ding, Yan, and Wang, Sam S. Y. (2011). Modeling of Wave-Current Interaction Using a Multidirectional
Wave-Action Balance Equation, In: Proceedings of The International Conference On Coastal
Engineering, No. 32 (2010), Shanghai, China. Paper #: waves.47. Retrieved from
http://journals.tdl.org/ICCE/
Ding, T. (2012). Developing a parametric model for hurricane wind and storm surge prediction in the
Gulf of Mexico, 2012 Water Environment Federation Technical Exhibition and Conference, New
Orleans, LA, Sept. 29-Oct. 3, 2012, (Available at
http://dl.dropbox.com/u/36531386/Ding_Hurricane.pdf)
Ding, Yan, Altinakar, S. Mustafa, Jia, Yafei, Kuiry, Soumendra N., Zhang, Yaoxin, and Goodman, Al
(2012a), “Simulation of Storm Surge in the Mississippi Gulf Coast Using an Integrated Coastal
Processes Model”, In: World Environmental and Water Resources Congress 2012: Crossing
Boundaries, Proceedings of ASCE-EWRI 2012 Congress, Albuquerque, New Mexico, May 20-24,
2012, pp1635-1652.
Ding, Yan, Rusdin, Andi, Kuiry, Soumendra N., Zhang, Yaoxin, Jia, Yafei, and Altinakar, Mustafa S. (2012b).
Validation of an integrated coastal processes model by simulating storm-surge and wave in the
Mississippi/Louisiana Gulf Coast, In: Proceeding of 3rd Int. Symp. On Shallow Flows, Iowa City, USA,
June 4-6, 2012 (12 pp in CD-ROM).
Ding, Yan, Kuiry, Soumendra N., Hossain, A.K.M Azad, Jia, Yafei, and Altinakar, Mustafa S. (2012c).
Simulation of Flood Flow in a Coastal Floodplain due to River Flood, Presentation in 2-Dimensional
Modeling Symposium Challenges – Floodplain Management Association, Sept. 4, 2012.
18
Ding, Yan, Yeh, Keh-Chia, Chen, Hung-Kwai, Wang, Sam S.Y. (2013a). “Coastal and Estuarine Planning for
Flood and Erosion Protection Using Integrated Coastal Model,” in: Coastal Hazards − Trends in
Engineering Mechanics , Wenrui Huang et al. eds., ASCE, pp163-176 (ISBN978-0-7844-1266-4).
Ding, Yan, Kuiry, S.N., Elgohry Moustafa, Jia, Y., Altinakar, M.S., and Yeh, K.-C. (2013b). Impact
Assessment of Sea-Level Rise and Hazardous Storms on Coasts and Estuaries Using Integrated
Processes Model, Ocean Engineering, Accepted, In Press.
http://dx.doi.org/10.1016/j.oceaneng.2013.01.015
Ding, Y., Ding, T., Jia, Y., Altinakar, M. S. (2013c). Developing a Tropical Cyclone Parametric Wind Model
with Landfall Effect for Real-Time Prediction of Wind and Storm Surge, In: Proceedings of 2013
IAHR Congress, Tsinghua University Press, Beijing, Chengdu, China, Sept. 8-13, 2013, 14 p.
Federal Emergency Management Agency (2009), HAZUS-MH MR4 flood model Technical manual,
Available at http://www.fema.gov/library/viewRecord.do?id=3726
Hossain, A.K.M. Azad, Jia, Yafei, Chao, Xiabo, and Ding, Yan (2013). Incorporation of CCHE-Coast flood
simulation with HAZUS, NCCHE Technical Report, NCCHE, 2013.
Jia, Y., Wang, S. S. Y., and Xu, Y. C. (2002). Validation and application of a 2D model to channel with
complex geometry, Int. J. Comput.Engineering Science, 3(1), 57-71.
Kuiry, S. N., Ding, Y., and Wang, S. S. Y. (2010), Modeling coastal barrier breaching flows with wellbalanced shock-capturing technique, Computers & Fluids, 39(10), pp2051-2068.
Svendsen, I.A. (1984). “Mass flux and undertow in a surf zone”, Coastal Engineering, 8(4), 347-365.
Svendsen, I. A., Haas, K., and Zhao, Q. (2003a). “Quasi-3D nearshore circulation model SHORECIRC –
Version 2.0”, Technical Report, Center for Applied Coastal Research, University of Delaware,
Newark, DE19716.
Svendsen, I. A., Qin, W., and Ebersole, B.A. (2003b). “Modelling waves and currents at the LSTF and
other laboratory facilities”, Coastal Engineering, 50(1-2), 19-45.
Zhang, Y.X., and Jia, Y. (2005). CCHE2D Mesh Generator – User’s Manuel Ver. 2.6, Technical Report No.
NCCHE-2005-05, National Center for Computational Hydroscience and Engineering, University of
Mississippi, University, MS. (http://ncche.olemiss.edu/index.php?page=freesoftware#mesh)
19