strange results from the TRIGRS model

[RubyZhao0222]

I used the TRIGRS model to simulate the evolution of the factor of safety under various rainfall events. However, I found a strange phenomenon, the FS value always has a sudden decrease before it is smaller than 1(see figure 1). I checked the TRIGRS manual these days and tried to give it a good explanation, however, I failed. I am wondering whether you know the possible reason or there are any problems with the simulation. Thanks very much.

[ghost]

No one has reported this issue before and I do not recall seeing it in any simulations I have run. To investigate this, I would need information about what inputs and options you were using. Please send me a copy of the TRIGRS log files from one or more of the simulations in the plot you sent.

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________________________________ From: RubyZhao0222 ***@***.***> Sent: Tuesday, June 13, 2023 4:45 AM To: usgs/landslides-trigrs ***@***.***> Cc: Subscribed ***@***.***> Subject: [EXTERNAL] [usgs/landslides-trigrs] strange results from the TRIGRS model (Issue #16) This email has been received from outside of DOI - Use caution before clicking on links, opening attachments, or responding. I used the TRIGRS model to simulate the evolution of the factor of safety under various rainfall events. However, I found a strange phenomenon, the FS value always has a sudden decrease before it is smaller than 1(see figure 1). I checked the TRIGRS manual these days and tried to give it a good explanation, however, I failed. I am wondering whether you know the possible reason or there are any problems with the simulation. Thanks very much. [figure1]<https://user-images.githubusercontent.com/127189260/245447892-d104d937-d339-4714-940f-c9ac519147e9.jpg> — Reply to this email directly, view it on GitHub<#16>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AEJYWGDWUP7K4QIMD7LOKZDXLBAFRANCNFSM6AAAAAAZEVHP24>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[RubyZhao0222]

Thanks for your reply. I have found what causes this phenomenon. The 'sudden decrease' occurs when the top of capillary fringe exceeds the ground surface in the case of selecting psi0=-1/alpha.

However, another problem confuses me. I found the actual infiltration rate calculated by Trigrs is the minimum values of precipitation rate and saturated hydraulic conductivity. This is correct for saturated zone. However, I used the unsaturated infiltration model, where I think the infiltration rate should be the minimum values of precipitation rate and infiltrability, and the infiltrability is not equal to saturated hydraulic conductivity for the unsaturated initial conditions. Do I overlook any model assumptions? Hope for your reply. Thanks very much.