Crest Level Design: Marine and Coastal Engineering - 01

 

1) What “crest level design” must satisfy at FEED

Crest elevation is not “one formula”. It is the highest of several controlling requirements:

1. Hydraulic performance

• limit mean overtopping discharge $q$ (and/or individual overtopping volumes) for the asset function

• limit run-up exceedance and freeboard under design sea state

2. Structural/geotechnical robustness

• allowance for settlement / consolidation / rock rearrangement

• allowance for construction tolerance (as-built variability)

• allowance for sea-level rise (project life)

3. Operational / functional

• crest used as access road? utilities corridor? emergency access?

• allowable “green water” / spray conditions for people/vehicles/equipment

Guidance commonly used for this methodology is EurOtop (overtopping/run-up) and the Rock Manual / rubble mound design practice.

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2) FEED inputs you must define (minimum set)

A. Design water levels (vertical components)

You need a Design Still Water Level (DSWL) for the storm condition:

$$\text{DSWL} = \text{Tide level (e.g., HAT or MHWS)} + \text{Storm surge} + \text{Wave setup} + \text{SLR allowance}$$

• Tide range near Abu Dhabi is of order ~1–1.5 m (you’ll confirm from an approved hydrographic source later; at FEED you can bound it conservatively).

• Add storm surge (site-specific; FEED: take a conservative bound)

• Add wave setup (often 0.1–0.3 m for many rubble structures, but treat as a term you include explicitly)

• Add SLR allowance per client policy (common FEED practice: pick an allowance for design life, e.g., 0.3–0.6 m depending on horizon)

Deliverable at FEED: a table of levels relative to a datum (CD / MSL / LAT) with chosen conservatisms and justification.

Full article here in Pdf.