Why WEMo

Powerful wave analysis without the modelling barrier

WEMo makes quantitative wave energy analysis accessible to coastal scientists, environmental professionals, resource managers and restoration practitioners who are not specialists in numerical wave modelling. It handles the technically demanding steps for you, so you can focus on what the waves mean for your site and your decision.

Create a free account See the results against SWAN
AccessibleNo computational grids, spectral boundary conditions or convergence tests. Draw an area and run.
Accuracy suited to the decisionEnough accuracy for siting, restoration, planning and screening, without needless numerical complexity.
Checked against SWANTuned against the standard spectral wave model, then tested on water it was not tuned on and against wave buoys.

Designed for scientists and practitioners

Built for people who know their coast, not their solver

Many of the people who most need wave information understand their coastal environment and their management questions well, but have no training in hydrodynamic or spectral wave modelling. WEMo is built for them.

What WEMo takes care of

  • Spatial setup: a grid of sites over the water at the spacing you choose.
  • Bathymetry: built-in depths, or your own survey.
  • Wind: decades of hourly wind over water, or a nearby buoy or station.
  • Fetch and wave growth: traced in up to 56 directions over the real depths.
  • Outputs: maps, exposure classes, a PDF report and GIS files, with sensible defaults throughout.

Where it is most useful

Estuaries, lagoons, lakes and other shallow or semi-enclosed coastal waters, where most of the waves are raised by the local wind. Its results support:

Habitat assessmentSeagrass and wetland restorationLiving shoreline planningSediment stabilitySite selectionComparing coastal conditionsAquaculture siting
Wave exposureFive classes, very sheltered to very exposed
Wave energyRepresentative wave energy (RWE) and wave height
Orbital velocityHow hard waves move the water at the bed
Bed shear stressThe force that can stir up or move sediment

Accuracy appropriate to the application

More complex is not always more accurate

Accuracy and precision are different things, and the model you need depends on which one your question turns on.

Accuracy

How well the results represent the conditions you care about: which sites are exposed, which are sheltered, and by how much.

Precision

How much detail and resolution the results carry: the full wave spectrum, every process, at every point in time and space.

When the aim is to find relative exposure, tell high-energy from low-energy places, judge habitat suitability or sediment stability, compare restoration sites, or see how wave conditions change, WEMo gives estimates accurate enough for the decision. The extra precision of a full spectral wave model often would not change that decision.

The right model depends on the question being asked and the resolution it needs, not on which model is more complex.

WEMo and SWAN

Two models for different needs

WEMo is not a replacement for Delft3D-WAVE or SWAN. It occupies its own, complementary space.

WEMo

Wave exposure for environmental and coastal management decisions

Built for
Screening, siting, restoration and planning across whole bays, estuaries and lakes, by scientists and practitioners.
What it needs from you
An area drawn on a map. Depths, wind and defaults are built in; your own data can replace them.
What you get
Wave exposure, energy, orbital velocity and bed shear stress at thousands of sites, weighted by years of wind, in minutes.
Precision
A scientifically based fetch model with the main shallow-water physics, at the accuracy these decisions need.

SWAN

Detailed spectral modelling for engineering and complex wave fields

Built for
Engineering design, complex offshore-to-nearshore wave transformation, and studies that depend on detailed spectral characteristics.
What it needs from you
A computational grid, bathymetry, wind fields and boundary conditions, plus calibration, validation and specialist training.
What you get
The full directional wave spectrum and its evolution through generation, propagation, transformation and interaction processes.
Precision
Greater numerical and spectral resolution, where the site or the consequences of the decision call for it.

The difference is not simply "simple versus sophisticated" or "less accurate versus more accurate". WEMo gives the accuracy needed for many environmental, restoration, planning and screening decisions with much lower technical and training barriers. SWAN gives greater numerical and spectral precision when the complexity of the site or the consequences of the decision require it.

Results compared with SWAN

Checked against the standard spectral model, and against measurements

WEMo's defaults were tuned against SWAN at 939 sites in the lower Chesapeake Bay. They were then tested, unchanged, over the whole bay, ten times the area, with both models on identical depths and steady winds from eight directions.

97%of 24,586 site–wind pairs across the whole Chesapeake Bay within 20% of SWAN at 10 m/s
0.99median ratio of WEMo to SWAN wave height at 10 m/s
0.06 mroot-mean-square difference from SWAN at 10 m/s (R² 0.97)
31wave buoys compared hour by hour over 2022–2024, in four basins
Two density scatter plots of WEMo against SWAN significant wave height at 24,586 site–wind pairs in Chesapeake Bay. At 10 m/s the points hug the one-to-one line: median ratio 0.99, 97% within 20%, RMSE 0.06 m, R² 0.97. At 20 m/s they fall slightly below it for the largest waves: median ratio 0.86, 73% within 20%, RMSE 0.50 m, R² 0.82.
WEMo against SWAN across the whole Chesapeake Bay. Each hexagon counts site–wind pairs; the solid line is perfect agreement and the dashed lines ±20%. At 10 m/s (left) WEMo matches SWAN closely across the full range of wave heights. At 20 m/s (right) the larger waves in deep, open water come out lower than SWAN's.
Two maps of Chesapeake Bay coloured by the ratio of WEMo to SWAN wave height. At 10 m/s most of the bay is close to 1 (white to pale blue). At 20 m/s the bay is mostly 0.8 to 1, with the open Atlantic offshore deeper blue.
Where the two agree. WEMo ÷ SWAN wave height at every site. Inside the bay, where WEMo is meant to be used, most sites sit close to 1 at both wind speeds; the open ocean at 20 m/s is where WEMo runs lowest.
Bar chart of mean wave height over 2022–2024 at eleven NOAA buoys in and around Chesapeake Bay, comparing measured values with WEMo. WEMo driven by wind over water tracks the measured heights from about 0.1 m at Jamestown to about 1.4 m at Virginia Beach.
Against real waves. Mean wave height over 2022–2024 at NOAA buoys inside Chesapeake Bay and at its mouth, measured (black) and from WEMo run hour by hour (green; grey with the earlier land-cell wind). r is the correlation with the measured record.

Known limits. In deep water with strong winds WEMo stays 14–20% below SWAN, yet within 6% of Kahma and Calkoen's (1992) growth curve from field measurements, which SWAN itself exceeds by about 20%. SWAN is a model, not a measurement, so a gap between the two is not automatically WEMo's error. The limitations set out where WEMo should not be relied on.

For WEMo side by side with SWAN, NOAA's original WEMo and other fetch-based tools, see how WEMo compares.

Which to use

Pick the model the question needs

WEMo fits when you need to…

  • Compare wave exposure across many sites in a bay, estuary, sound or lake.
  • Screen sites for seagrass, oyster reefs, wetlands, living shorelines or aquaculture.
  • Judge sediment stability from orbital velocity and bed shear stress.
  • Summarise years of wind into one map and report, quickly and consistently.

Use SWAN or another detailed model when you need…

  • Engineering design conditions, with a coastal engineer.
  • Complex offshore-to-nearshore wave transformation.
  • Waves through a particular storm, hour by hour, with currents or wave setup.
  • Results that depend on the detailed shape of the wave spectrum.

Try it on your own water

Free during early access. Questions, demos or a custom study? [email protected]

Create a free account How it works