Dean Profile uses

[MikeWalkden]

_Start of (Email) message from Dave FM.
I've changed CME today to use mean SWL for beach Dean profiles. Mean SWL is the start-of-simulation SWL plus any long-term change in SWL. This-iteration SWL (as used elsewhere in the model, e.g. in coastline tracing) is the same, plus any tidal change in SWL.

• Beach Dean profiles start at mean SWL plus the user-input berm height.
• Cliff collapse Dean profiles do not consider SWL. Instead they start at an elevation calculated using the user-input "Minimum height of landward talus end, as fraction of cliff elevation [< 1]".
  All OK so far? Right, two weeks ago in Southwark we discussed also using runup to determine beach Dean profile start elevation, as calculated by CShore. We have this available, thanks to Manuel. So my questions are:
• Do we still wish to do this?
• If so, it would be easy enough to save a runup value for every coast point, and use this in the calculation of beach Dean profile start elevation.
  Your thoughts?
  Dave
  End of Email message._

The point on runup and the origin of the Dean profile has, I think, since been covered by the ‘SWL and runup‘ discussion.

The use of mean SWL + the user-input berm height as the origin of the Beach Dean profiles makes sense to me.

Personally, I don’t think it’s a good idea to represent the talus from cliff failure as a Dean profile. I think this brings unrealistic irregularity to the coastline and nearshore. In my mind, talus tends to form a cone or wedge at the toe of the cliff, which is then weathered by waves. The products of that weathering are then either lost in suspension or accumulate in the beach. So the question for me is whether to represent the cone/ wedge stage, which requires modelling the form and rates of loss, or to pass the beach suitable material directly into the beach.

In SCAPE I chose to represent a wedge of talus and to weather it, assuming (I think) that its resistance to wave attack was reduced to 10% of the original. In practice I do not know whether this was better than passing the beach suitable material directly into the beach. In most cases I suspect not - I could outline the pros and cons if helpful?