Southern California Coastal Hazards

Primary components

• High resolution Digital Elevation Model (DEM)
  • Fill-in technology
• Spectral wave model
• Model prediction system (MOP)
  • Tide model
  • CoSMoS—Coastal Storm Modelling System
  • Other models
    • Surge model
    • Run-up model
    • Longshore transport model
    • Profile change model
    • Probabilistic cliff failure model

High resolution Digital Elevation Model (DEM)

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Fill-in technology

An all-terrain vehicle (ATV, above) is used to collect topographic surveys of the beach. These surveys are conducted with differential GPS (DGPS- accuracy ~2 cm horizontal and vertical) for monitoring seasonal beach changes and assessing lidar accuracy. A map of the ATV survey lines is shown at right.
A Real Time Kinematic Differential Global Positioning System (RTK-DGPS) mounted on a personal watercraft (PWC, above) is used to collect bathymetric horizontal and vertical position data in the study area. A map of the PWC survey lines is shown at right.

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Spectral wave model

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Model prediction system (MOP)

CoSMoS—Coastal Sorm Modelling System

http://cosmos.deltares.nl/SoCalCoastalHazards/index.html (Please note: this web site does not appear to work on Macintosh platforms--just Windows PC.

The CoSMoS system for Southern California has been set up as part of the USGS Southern California Coastal Hazards project. The system consists of several numerical models that generate real-time forecasts of water levels, wave heights, coastal erosion and flooding for a period of up to 3 days in advance. The latest model predictions are posted on this website every 12 hours.

In addition to making real-time forecasts, the CoSMoS system has also been applied to simulate a number of historical storms and hypothetical scenarios.

About the CoSMoS System

Models

Workflow

Hydrodynamic models

Delft3D is a open source 2D/3D modelling system to investigate hydrodynamics, sediment transport and morphology and water quality for fluvial, estuarine and coastal environments.

The software has proven its capabilities in many places around the world, such as the Netherlands, USA, Hong Kong, Singapore, Australia, Venice, etc. It is continuously being improved and developed with innovative advanced modeling techniques. Visit delftsoftware.wldelft.nl to read more.

XBeach

The XBeach model can be used as stand-alone model for small-scale (project-scale) coastal applications, but will also be used within the Morphos model system, where it will be driven by boundary conditions provided by the wind, wave and surge models and its main output to be transferred back will be the time-varying bathymetry and possibly discharges over breached barrier island sections. The model solves coupled 2D horizontal equations for wave propagation, flow, sediment transport and bottom changes, for varying (spectral) wave and flow boundary conditions. Because the model takes into account the variation in wave height in time (long known to surfers) it resolves the special long wave motions created by this variation. This so-called 'surf beat' is responsible for most of the swash waves that actually hit the dune front or overtop it. Because of this innovation the XBeach model is better able to model the development of the dune erosion profile and to predict when a dune or barrier island will start overwashing and breaching. Visit xbeach.org to read more.

Wave models

SWAN: Simulating WAves Nearshore

In many engineering studies, knowledge of the operational or of the extreme wave conditions in coastal waters (which may include estuaries, tidal inlets, barrier islands with tidal flats, channels etc.) is required. To obtain realistic estimates of random, short-crested wind-generated waves in such conditions for a given bottom topography, wind field, water level and current field, the numerical wave model SWAN can be used. This SWAN model is a third-generation stand-alone (phase-averaged) wave model for the simulation of waves in waters of deep, intermediate and finite depth. It is also suitable for use as a wave hindcast model. www.wldelft.nl/soft/swan/

WAVEWATCH III

WAVEWATCH III (Tolman 1997, 1999a) is a third generation wave model developed at NOAA/NCEP in the spirit of the WAM model (WAMDIG 1988, Komen et al. 1994). It is a further development of the model WAVEWATCH I, as developed at Delft University of Technology (Tolman 1989, 1991) and WAVEWATCH II, developed at NASA, Goddard Space Flight Center (e.g., Tolman 1992). WAVEWATCH III, however, differs from its predecessors in many important points such as the governing equations, the model structure, the numerical methods and the physical parameterizations. Visit polar.ncep.noaa.gov/waves/index2.shtml or polar.ncep.noaa.gov/waves/wavewatch/wavewatch.shtml for more information.

Meteo models

Global Forecast System

The Global Forecast System (GFS) is a global numerical weather prediction computer model run by NOAA. This mathematical model is run four times a day and produces forecasts up 16 days in advance, but with decreasing spatial and temporal resolution over time (it is widely accepted that beyond 7 days the forecast is little better than guesswork).

The model is run in two parts: the first part has a higher resolution and goes out to 180 hours (7 days) in the future, the second part runs from 180 to 384 hours (16 days) at a lower resolution. The resolution of the model varies in each part of the model: horizontally, it divides the surface of the earth into 35 or 70 kilometre grid squares; vertically, it divides the atmosphere into 64 layers and temporally, it produces a forecast for every 3rd hour for the first 180 hours, after that they are produced for every 12th hour.

Tide model

Delft3D Hydrodynamic Module Boundaries from global tide model Series of overlapping curvilinear grids Water level output at each MOP station

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Other models

• Surge Model- analytical approaches presented by Jelesnianski (1972) and Hsu (2004), that rely on estimates of the shoaling factor, sea level pressure, and a correction factor for storm approach
• Run-up Model- empirical formulations of Ruggiero et al. (2001) and Stockdon et al. (2006)
• Longshore Transport Model- CERC Formulation
• Profile Change Model- UNIBEST DE (dune erosion)
• Probabilistic Cliff Failure Model- in development by Collins and Hapke, USGS