Per-Object Water Depth Override Now Available

Risk studies rarely have a single, neat water depth.  A drilling deck might span a narrow window of depths, but the individual lifts you simulate often happen at very specific spots — directly above a wellhead at 500 m, or over a manifold at a known fixed depth that has nothing to do with the wider study range. Until now, every drop on a study used fixed water depth from the study's water depth setting.

DORAS now lets you set a Custom Water Depth directly on individual objects. When this field is set, that object — and only that object — is dropped at the depth you specify, regardless of the study's wider depth range.

Where to find it

Open any object record in the Objects list. You'll see a new Custom Water Depth (m) input sitting immediately below the existing Custom Cone Angle (Degrees) field. The field accepts values from 0 to 2000 m and defaults to 0, which means "use the study water depth as normal."

When to use it

Reach for this field whenever you know that a particular object will land at a depth that doesn't match the rest of your study. Some common scenarios:

• An object lifted directly above a subsea wellhead below the water line
• A subsea component being lowered into a known basin or trench
• A scenario where the dropped object's seabed landing point sits well outside the typical study water depth window
• Any case where the actual fall distance is fixed and known, rather than randomly distributed

Leave the value at 0 for any object whose drop conditions are well represented by the study's overall depth range. The override is only there for the cases where it's actively needed.

What changes when you set a value

Setting a custom depth doesn't just shift the geometric cone radius — DORAS uses the same depth value consistently across all of the physics calculations for that object's drops. Specifically, the custom depth flows into:

• Lateral excursion — the 1σ, 2σ and 3σ cone radii that describe where the object can land
• Kinetic energy at impact — deeper drops give the object more distance to accelerate
• Current-induced dispersion — when "simple current effects" is enabled, fall time scales with depth

Because the depth is fixed rather than sampled, every drop event for that object will produce the same lateral deviation. You'll see this clearly in the calculation tables: instead of a spread of values, the object's cone radius rows become deterministic.

A note on flat objects

DNV-RP-F107 caps the effective water depth at 180 m for flat or long objects, on the assumption that beyond that depth a flat object reaches a stable terminal trajectory and additional fall distance no longer increases its lateral spread. When you supply a custom depth, that cap is intentionally bypassed — DORAS treats your explicit value as authoritative, on the basis that you know more about the specific drop than the conservative class-level rule does. Use this carefully and only when it genuinely reflects the physical situation you're modelling.

Trying it out

The change is live now. Open any object, enter a custom depth, save, and re-run Calculate. You'll see the object's cone radii in the Drop Analysis tables update to reflect the depth you've supplied, while every other object continues to use the study's water depth range as before. Reset the field to 0 at any time to return to the default behaviour.

As always, more granular control is only useful when it reflects something real about your scenario — but when it does, this small addition can meaningfully sharpen the results of a study that previously had to paper over depth variation with a single global range.