Bank erosion

[Kien Nguyen Thanh]

Good morning Tom & everyone,

I am trying to simulate the land evolution for one site as in the DEM. The simulation for 4 years by CAESAR-Lisflood results in elevation differences up to 7m, which is surreal compared to the observation. I also noticed that most erosion happened on the banks of the channel. The magnitude of this bank erosion seems to be extremely high. 

Do anyone have any advice for understanding and modifying this bank erosion?

Cheers,

Kien.

[tom.co...@gmail.com]

Hi Kien – first Q is do you have the lateral erosion check box ticked? If yes the answer lies in there if no it’s a different set of possibilities..

Tom

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[Kien Nguyen Thanh]

Hi Tom

Thanks for your response.

Yes I do have the lateral erosion check box ticked. It is intuitive to have more erosion at the bank, but a 7m elevdiff over 4 years of simulation is not real. I attached here the configuration file for your reference.

I am trying to understand what factors impact the bank erosion. Can you share what the different set of possibilities are?

Regards.

[Kien Nguyen Thanh]

Hi Tom

Further to the previous email, I tried to set the creep rate, soil erosion rate and lateral erosion rate (with the lateral erosion checkbox ticked) to 0 to see what erosion the software would return. The bank/edge erosion still resulted in up to 7m elevdiff. Do you have any insights for this?

I am sharing the simulation data in the attached file for reference. 

https://drive.google.com/file/d/1tEpVOssG_KCyqKIsFDqOjia4IoUisN2G/view?usp=drive_link

Kien.

[Tom Coulthard]

Hi Kien - is this 7m on one cell or a few or a few tens of cells?

On 4 Jul 2023, at 04:32, Kien Nguyen Thanh <thanh...@gmail.com> wrote:



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[Kien Nguyen Thanh]

Hi Tom

It happens everywhere as shown below. 

I am trying to read your code to understand. But can you share what factors impact the erosion on the bank/edge?

[Kien Nguyen Thanh]

Hi Tom

I am going through your code. It seems to be that the erosion happening in the following functions: 

(1) erode(): controlled by Wilcock/etc. modelling

(2) lateral3()

(3) slide_3(): local landslides

(4) creep(): controlled by creep rate

(5) soilerosion(): controlled by soil erosion rate

(6) slide_5(). 

I did not use dune and soil development options.  

I am trying to understand which factor contributes most. It seems that the erode() with the Wilcock and Crowe (which I am using) causes the majority of the erosion. 

[tom.co...@gmail.com]

Tried reducing the lateral erosion rate to zero? Then gradually work upwards?

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[Kien Nguyen Thanh]

Yes I set lateral erosion rate, creep rate, soil erosion rate all to 0. I also commented out the slide_3 and slide_5 functions to investigate the main contribution of the bank/edge erosion. That shows that the erode() causes the most erosion. 

[Kien Nguyen Thanh]

Hi Tom,

Are you able to advise what constitute the total erosion? To fill in: Total erosion = lateral erosion + creep erosion + soil erosion + ... 

And also just to confirm: does CAESAR Lisflood deal with both sheet rill and gully erosion?

Thank you.

[tom.co...@gmail.com]

HI – erosion can happen via slope processes (slides, creep) and within the fluvial component via bed erosion, lateral erosion or ‘in channel erosion’ which is a parameter that accounts for lateral collapse within a channel (wetted area)

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