High sediment export values SDR

Hi there,
I just ran the SDR model for my watershed (Willamette Basin) and got extremely high sediment export values (6 million tonnes per hectare). Any thoughts on where to start looking first as to what could make this value so astronomically high? All other values are also high.

Looking at the soil erodibility and rainfall erosivity the values seem high, even after soil erodibility was converted to the appropriate units.

Soil erodibility on my map range from 8025-370970.
Rainfall erosivity on my map ranges from15831-36819.

The output files are attached as google drive folders. Any insight is appreciated!



Thank you in advance.
Kind regards,

Hi @michelle.vanhilten -

The usual values for soil erodibility are less than 1.0, so I’m not sure how your erodibility map was created, but perhaps there was a conversion from polygon to raster, where the wrong column got used as the raster values? Take a look at the User Guide Appendix, you’ll see a table of typical values (in US units, which are even smaller when converted to metric).

Rainfall erosivity values are generally lower, although I’ve seen some pretty high values, depending on how it’s calculated, and if it’s a place with strong storms. Where did your erosivity values come from?

~ Stacie

Hi Stacie,
Thanks for the response. I looked into my K factor map and it was using the MUKEY field in the map as opposed to k factor. So I’ve got this sorted and have it mapping the K factor now and the numbers look normal (between 0 and 1). I am running into an issue converting this to metric though. Raster calculator, field calculator, and times don’t seem to work. When I use raster calc and times, I get numbers higher than before and field calc doesn’t run at all. I believe this is because the K fact field in the attribute table is set as ‘string’. Do you have any idea how I convert the units given this information or how you might have handled this using this particular data for k factor? PS, I’ve used the soil development data toolbox and accompanying data, as recommended for the US.

In regards to rainfall erosivity, I retrieved my data from https://esdac.jrc.ec.europa.eu/content/global-rainfall-erosivity. If you think it is a bit high, but not alarmingly high, it might make sense because my study area (Western Oregon) is known for stormier weather.

One option is to create a new field that’s floating point, copy the K values from the text field into the floating point field, then convert to metric with the floating point field.

~ Stacie

1 Like