User Forum of Software BASEMENT

LydiaSeitz

User

Registered: 2014-09-08

Posts: 18

How to force erosion?

Hi there,

I have too much deposition on some of my cross sections and I am wondering how I can force erosion on these spots. I tried to vary the "bottom_range" to minimize the range where bed load is transported but it just reduces the deposition and does not lead to erosion. Changing the Shields coefficient or the "bed_load_factor" is changing the transport behavior globally for the whole model. Is there any parameter to change the transport behavior locally or to force erosion locally?

Thanks for your help!

Best wishes
Lydia

Lukas Vonwiller

Developer

Registered: 2014-09-04

Posts: 130

Re: How to force erosion?

Hi Lydia

In the topography file you have the possibility to manipulate your cross sections and define certain values only for single cross sections such as for example 'theta_critic', 'bed_form_factor', and 'friction_calibration_factor'.
I will update and improve the description for these tags for the next release (coming soon).

Please let us know if you have further questions.

Best wishes
Lukas

LydiaSeitz

User

Registered: 2014-09-08

Posts: 18

Re: How to force erosion?

Dear Lukas,

thanks a lot for your fast reply. Now I tried the theta_crit for a single cross section but I still have some questions about it.

For the theta_crit in the geometry file there is a range given for the value ranging from -1.1 - 1.0 with a default value of -1.0.  Now I set the value to 1.0, just to see what happens but there was no change in this specific cross section. Usually I defined the theta crit around 0.035 - 0.047 depending on the situation. Did I misunderstood anything? I couldn´t find further explanation in the user manual on how this theta crit is implemented. What does the theta crit of -1.0 mean?

Hope you can help me again.

Best wishes
Lydia

Lukas Vonwiller

Developer

Registered: 2014-09-04

Posts: 130

Re: How to force erosion?

Hi Lydia

theta_crit of -1.0 means that the theta critical defined in the BEDLOAD-PARAMETER block is used and you do not change anything in this cross section (default behaviour).
If you define values between 0.0 and 1.0, you can change your theta_crit locally for this cross section.
However, to force erosion you have to choose small theta_crit (e.g. 0.015).

Hope this helps!
Lukas

LydiaSeitz

User

Registered: 2014-09-08

Posts: 18

Re: How to force erosion?

Dear Lukas,

thanks again for your help! It helped a lot!

Now there is erosion on the cross section. I used theta_crit = 0.025 because a value of 0.015 caused too much erosion. 

Best wishes
Lydia