Determination of the thalweg from SRR method

[Delogit2021]

Dear all,

I am trying to adapt the code you shared here in order to compute the thalweg for some branches of a river. I will try to summarize the main points here:

• the goal I want to reach is to determine the thalweg for some of the branches that make up the Po lagoon starting from a DEM with bathymetric data inside (I attach you a screenshot of the investigated area, all_Po_lagoon.png). I produced dedicated DEM for each branch so to allow the code to evaluate the thalweg separately (I will also send you an example, one_branch.png). I send you also and example of the DEM I produced, so you can check if it is correct for the tool;

• not interested in flooding events;

• I have only a single starting point, which represents the mouth of the river, from which I have to start to evaluate thalweg for a specific branch. Given that, what 'starting points' refer to in the code? Should I remove the maximum_extent_map from my code, because I am not interested in flood events, and directly give the coordinates of the starting point to the function that computes thalweg?

Hope you could help me.

Best regards,

Alessandro

DEM_attempt2.tif.zip

[yuerongz]

1. I would recommend that you do not crop your DEM, or at lease leave enough buffer for both sides of the river of interest. Because the algorithm will stop when any NAN value exists in the searching window. The boundary of your DEM is not enough for the algorithm to perform a proper search.
   A more serious problem is with your DEM data. If you have instpected it in any GIS software (like QGIS), you would find that your river elevation is higher than the bank elevation. The bank elevation sits at -4 metres minimum, which is 4 metres below the sea level. I don't think this would be a normal case for a river bank.
   And the data does not have a proper projection system (for example, EPSG:4326), which the algorithm requires.
2. that's fine.
3. The sdr_Searching_MCL function in https://github.com/yuerongz/SRR-method/blob/master/SDR_programs_call.py should suit your purpose.
   starting_coordinates for this function should be a tuple of the X, Y coordinates of the highest point of the thalweg. They need to be in the same projection system as your DEM.
   e.g.,
   starting_coordinates = (145, -30) # if your DEM file projection system is in (longitude, latitude), like EPSG:4326.

[yangmoudashuaibi]

Dear Professor Zhou,

My name is Haoyi Yang, a Master’s student at Yangzhou University. I have recently been studying your SRR-method and referring to your GitHub repository (SRR-method), which I find highly relevant to my research.

I am currently attempting to apply this method to my own dataset. However, I have encountered repeated errors during the implementation, which I suspect may be related to data format or preprocessing. To better understand the expected input format, I was wondering if you could kindly provide the DEM data and maximum flood extent TIF files used in your study.

This would be extremely helpful for me to understand the correct data structure and preprocessing requirements. If sharing the dataset is not possible, any guidance on the expected data format would also be greatly appreciated.

Thank you for your time and assistance. I look forward to your response.

Best regards,
Haoyi Yang
Master’s student, Yangzhou University
Email: 420463209@qq.com