Sediment Load Series

[Anonymous]

Hi,

I am wondering if anyone can help me. I am trying to run a sediment model using “Sediment Load Series” as the input upstream. I have measured sediment data which I will be using at this location. Right now I am trying to understand what is happening so I am using a continuous sediment series and hoping to see it move through the river system.

When I enter the time series data for sediment in tonnes in the left hand-side of the sediment load series window (e.g. a continuous series of 1 tonne) and run the model I expect to see 1 tonne at the same cross section for the same time period in the “Mass In” column when I look at the sediment output tables. This isn’t the case however and the sediment gradation rating curve on the right hand-side of the sediment load series window seems to be important for determining this.

For example, if I enter data in the left pane but don’t indicate a gradation curve I get zeros in the “Mass In” column which is fine. However If I enter a continuous series of 1 tonne in the left pane and use a gradation curve with “1” as the “total load” and underneath I indicate the gradation, I still don’t get 1 in the “Mass In” output tables- I get a continuous input of 73 tonnes instead. I am using metric units but I have noticed that if I convert to US units then I will get 0.9996 tonne as the “Mass In”. If the number in the “total load” is anything other than 1 then the output will change despite the unit system used.

Can anyone explain to me how this works?

Thank you in advance if anyone can help.

Seán

[Anonymous]

Hi Seán,

i have the same issues right now and i have no idea how i can fix them.
But i have some information which can maybe help you:

-us tons are different from si tons
-i found out that the “mass in” output also depends on the computational increment time step, which is defined in the quasi steady flow data. That brings me to assumption that the definition of the sediment load could be wrong. The input should be “tons” but maybe it is “tons/hours” or something like that like it is defined usually in hec-ras. If i just change the computational increment, the “mass in” changes significant and thats weird.
-There could be an influence if the duration time of the sediment load is different than the duration time of the quasi steady flow or the computational increment

-i also dont really know how the gradation curve works. The definition is a bit strange because u first define a total load and use a gradation curve on it. From my point of view it would be much more useful if u define a load/timestep instead of a total load.

Thats all i can say right now…

Let me know if u found out something.

Michael

[Author]

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