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I am currently trying to simulate geomorphological change using T2D and GAIA. I want to consider both suspended load and bedload, however, bed evolution of almost over 500m deposition occurs at the first calculation time step. The attached screenshot is the first output step to find irregular deposition.
I have checked the calculation works fine in case only the bedload is activated.
Is there anyone who has experienced the same problem? Could you share your experience?
Thank you so much for reading and cooperation in advance!

Difficult to say from just this figure. Please make it a habit to add steering files if you asking for help. In this case I suspect it is a wetting and drying issue.
In addition, I assume it is the first output time step that shows this issue not the very first time step, as 71 mihutes is very large for a time step. Reducing the output time step will help visualising the source of the problem.

Thank you so much for your kind reply. I will attach the steering file from now on.
What I want to simulate is the flow and sediment deposition pattern within the dry dam reservoir that is mostly empty but inundates only during times of flooding.
The flow calculations I conducted are as follows.

1. Firstly, steady flow simulation is done for hot-start (steering file is t2d_nishinotani_steady.cas).
2. Secondly, start computing the unsteady flow by loading the hot-start file. At this point, I couple GAIA with T2D and begin the sediment calculation (steering file is 2d_nishinotani_steady.cas and t2d_gaia_nishinotani.cas).

At the boundary between the wet and the dry area, abnormal sediment deposition is occurring, so I believe it is a problem caused by the dry and wet issues as you mentioned.
Could you please give me some advice?

Start with turning tidal flats on in theGAIA steering file by removing the / in front of it. Do the same for the setting of the advection scheme to set it to 14.
/ SCHEME FOR ADVECTION OF SUSPENDED SEDIMENTS : 14
/ TIDAL FLATS : YES
you may also want to add
CONTINUITY CORRECTION = YES

All this is mentioned in the pink box on page 15 of the GAIA user manual.

Dear mafknappen

Thank you for your advice.
I modified the GAIA steering file by removing / in front of TIDAL FLATS and SCHEME FOR ADVECTION *** (attached here). However, I observed sediment deposition of nearly 1000 meters.

Besides that I added CONTINUITY CORRECTION, however, the following error message emerged.

... processing the steering file
~> Checking keyword/rubrique coherence
~> Checking keyword/rubrique coherence
Traceback (most recent call last):
File "C:\TELEMACV8P4\V8P4\scripts\python3\telemac2d.py", line 7, in <module>
main('telemac2d')
File "C:\TELEMACV8P4\V8P4\scripts\python3\runcode.py", line 288, in main
run_study(cas_file, code_name, options)
File "C:\TELEMACV8P4\V8P4\scripts\python3\execution\run_cas.py", line 163, in run_study
my_study = Study(
File "C:\TELEMACV8P4\V8P4\scripts\python3\execution\study.py", line 163, in __init__
cas_plage = TelemacCas(cas_name_cpl, dico_file_plage)
File "C:\TELEMACV8P4\V8P4\scripts\python3\execution\telemac_cas.py", line 110, in __init__
self._check_content()
File "C:\TELEMACV8P4\V8P4\scripts\python3\execution\telemac_cas.py", line 268, in _check_content
raise TelemacException(
utils.exceptions.TelemacException: Unknown keyword CONTINUITY CORRECTION in steering file C:\TELEMAC_WorkingDir\drydam\nishinotani\suspended_bedload\t2d_gaia_nishinotani.cas