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 Jbragger (Jbragger) posted on Friday, February 06, 2009 - 12:00 pm
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Hi
I have a few questions just in starting off using CAESAR, any help would be appriciated:-
1. Is the number of iterations equal to the number of years the model is simulating? As an a example, if I ran a simulation of 1000 iterations, would that be modelling change over 1000 years?
2. How does CAESAR use the rainfall input file? Will it automatically assume it is hourly data? Does it use the whole file every iteration, or just part of it in each?
3. The DEM that I have made is 6400kb, and from other posts on this board I assume that this would be runable, but when I try to run the model it comes up with a system out of memory error. Will using a better system potentially alliviate this problem?
4. Finally, how do I format the sediment size data file so that CAESAR will accept it?
Thanks in advance,
Joe |
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Hi Joe,
1. Is the number of iterations equal to the number of years the model is simulating? As an a example, if I ran a simulation of 1000 iterations, would that be modelling change over 1000 years?
Nope, iterations is how many model steps or iterations it takes. The time step in CASESAR is variable and shortens when there is too much erosion and deposition going on - then lengthens when there is less. It is set by the erodefactor variable - so it only allows a max amount of erosion and deposition per iteration defined by this value. THerefore, it may take 10000 iterations to run 1 year of simulation or 20000 if there is more erosion/dep going on.
2. How does CAESAR use the rainfall input file? Will it automatically assume it is hourly data? Does it use the whole file every iteration, or just part of it in each?
Yes, it assumes its hourly data. It uses the line of the file as a rainfall input. So line 10 is the input at hour 10, line 20 at hour 20 etc.. This data is then input in to the hydrological model. The output fromthe hydrological model is controlled mainly by the m value (there is some disussion about this on one of the papers).
3. The DEM that I have made is 6400kb, and from other posts on this board I assume that this would be runable, but when I try to run the model it comes up with a system out of memory error. Will using a better system potentially alliviate this problem?
Maybe, my advice is to start small. Typically DEM's with greater than 400 000 cells start to run a bit slower.. I would recomend getting things set up - or figuring out what you are doing with a smaller DEM to start with, or to re-sample your DEM to larger grid cells - thus reducing the total number of cells.
4. Finally, how do I format the sediment size data file so that CAESAR will accept it?
Not sure what you mean here. DO you mean the initial grainsize across the DEM? If so this is tricky.
Tom |
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| Jbragger (Jbragger) posted on Wednesday, February 11, 2009 - 01:29 pm
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Thanks Tom
A couple of further questions relating to this:
1. I can't find the option to edit the erodefactor variable. How can this be edited to change the length of time the model is represented?
2. I did mean the initial grainsize across the DEM, yes. I've found another post on this board which describes it and it does look tricky - is it possible to run the model without using a sediment grainsize model?
Cheers
Joe |
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Hi Joe,
On the numerical tab its "max erode limit". If you don twant to have variable grainsizes, just set everything to one grainsize... in the grain tab just make sure all the sizes are teh same,
Tom |
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| Jbragger (Jbragger) posted on Wednesday, February 18, 2009 - 01:54 pm
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Hi again Tom
Sorry to bother you again. I'm having a problem in actually running the model now. It keeps getting stuck at 41.69 days, after 1019 iterations. Altohugh it doesn't come up with an error message, it just doesn't do any further iterations - even when left all night. Do you have any idea why this might be occuring?
thanks
Joe |
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| is it the max time limit? is that set to 1000 hours (approx 42 days)? Should be in the numerical tab. If so raise that to - well however long you want it to run for! |
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| Jbragger (Jbragger) posted on Thursday, February 19, 2009 - 04:01 pm
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Thanks Tom, should have worked that one out myself.
One more (hopefully last!) problem, CAESAR is occasional crashing half way through a simulation with the message 'index was outside the bounds of the array'. I understand that this means it is trying to access value which arn't on the DEM? How can this be prevented?
Thanks
Joe |
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OK, not an especially easy one to answer this, but have you set 'Memory limit' in the numerical tab to 1? If not try it,...
Tom |
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