Set elevations, select controlling water level, compute crest. Add wave runup and settlement for safety. Download clean CSV and PDF reports for reviewers fast.
| Foundation Elev. | NWL | DFL | Freeboard | Wave | Settlement | Extra | Computed Crest |
|---|---|---|---|---|---|---|---|
| 512.400 m | 545.000 m | 552.200 m | 1.500 m | 0.800 m | 0.300 m | 0.100 m | 554.900 m |
| 1680.000 ft | 1790.000 ft | 1805.000 ft | 6.000 ft | 2.000 ft | 1.000 ft | 0.500 ft | 1814.500 ft |
This calculator estimates a preliminary dam crest elevation by adding allowances above a controlling water surface elevation (WSE).
Use project standards for how freeboard, wave run-up, and settlement are defined.
Dam crest elevation is set above the controlling water surface to limit overtopping. This calculator compares normal and design flood levels, or accepts a manual controlling stage, then adds allowances to reach a defensible crest. Using a single controlling stage avoids mixing criteria between operating and extreme events and keeps documentation consistent. Align the selected stage with operating rules and lead time. Document assumptions for routing method and hydrologic uncertainty to avoid disputes.
Freeboard is the vertical margin between the controlling water level and the start of additional effects. Agencies and owners often specify minimum freeboard bands by hazard class, consequence category, and evacuation time. Entering a higher freeboard increases crest elevation linearly, which can affect dam height, embankment volume, and outlet works elevations.
Wind setup and wave run-up can dominate crest requirements on wide reservoirs. The tool lets you enter wave run-up directly or estimate it from wind speed and effective fetch length. Longer fetch and stronger wind increase wave energy, raising run-up and the required crest. When available, use site-specific hindcast data and shoreline alignment to refine run-up.
Embankment settlement reduces crest over the service life, especially for compressible foundations and high rockfill content. The settlement allowance is added as a positive margin so the constructed crest remains adequate after deformation. Consider staged construction, instrumentation results, and post-construction monitoring to justify the settlement value used in design checks.
The calculator reports crest elevation, total allowance, and resulting dam height above foundation elevation. These outputs support cross-checks against spillway capacity, parapet needs, road grades, and freeboard standards. Exporting CSV helps track alternatives, while the PDF summary supports internal review, permitting submissions, and change-control records. Pair the crest result with drawings that show stationing, survey benchmarks, and datum conversions. Always verify units and rounding, and note whether allowances are conservative or probabilistic.
Use the highest stage that matches your adopted criteria: design flood, probable maximum flood, or an approved manual stage. The crest is then set above that stage with required allowances.
Enter the level you have and choose Manual/Selected as the controlling method. You can later update the normal and flood levels as routing results become available.
If you lack a detailed study, use the wind-and-fetch estimate as a screening value. Replace it with site-specific hindcast, physical modeling, or agency guidance when decisions become final.
No. Settlement allowance represents expected long-term loss in crest elevation. Construction overbuild is a method to achieve the target crest after settlement; document both if you use overbuild.
Dam height is reported from crest to foundation to reflect structural demand and fill quantity. If you report height from ground surface, adjust the foundation elevation to match your datum.
Yes for preliminary crest checks, because the equation is elevation-based. However, concrete dams often require additional checks for wave splash, parapets, and seismic freeboard that should be handled separately.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.