CAESAR-Lisflood and stiff clay soils

[Kelly Crowell]

Hello Professor Coulthard,

I have a fairly strong memory of reading a statement that CAESAR-Lisflood is not appropriate for cohesive soils, but I can't find that statement again. Perhaps it has been removed from an update? Or, not unlikely, I'm mistaken.

I see the lateral erosion rate is adjustable to affect the form of channels with narrow channels in a cohesive soil, but how does this interact with the grain size distribution? If clay-sized particles are mobilized based on the shear stress required to move them if not cohering to the bed wouldn't this still over predict incision?

I've experimented with piecewise planar profiles simulating a low-gradient clayey top slope leading to a steep bedrock side slope using grain size distributions determined by lab analyses and the top slope is ripped apart very quickly compared to what is seen in the field.

I'd appreciate your consideration and suggestions.

Cheers,

Kelly Crowell

[Tom Coulthard]

Hi Kelly. 

That’s a good question 😀 so the sed transport rules in CL are all for non cohesive sediment… so the short answer is CL isn’t appropriate for cohesive substrates. However - I’ve had some success modelling estuary muds (very cohesive) using the wilcock and Crowe eqtn. As this includes a hiding term (in effect if there is a lot of the finest fraction it ‘hides’ or restricts the entrainment of the larger grain sizes) this can operate in the same way as cohesion can. 

It’s also a good question - as all (all) sediment transport rules are not very good (being polite) when used on any data not used to develop them! So it’s all varying degrees of wrongness! 

I appreciate that may not help! 

---

From: 'Kelly Crowell' via caesar-lisflood <caesar-...@googlegroups.com>
Sent: Friday, January 17, 2025 8:18:20 PM
To: caesar-lisflood <caesar-...@googlegroups.com>
Subject: CAESAR-Lisflood and stiff clay soils

 

--
You received this message because you are subscribed to the Google Groups "caesar-lisflood" group.
To unsubscribe from this group and stop receiving emails from it, send an email to caesar-lisflo...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/caesar-lisflood/6125d252-3d42-4269-88eb-b15db487a2f9n%40googlegroups.com.