# What are the units of the SDR outputs **URL:** \ **Category:** Software Support\ **Tags:** sdr\ **Created:** [November 21, 2023, 10:39am UTC](https://community.naturalcapitalalliance.org/t/what-are-the-units-of-the-sdr-outputs/4274 "2023-11-21T10:39:51Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Willem](https://avatars.discourse-cdn.com/v4/letter/w/898d66/32.png) [@Willem](https://community.naturalcapitalalliance.org/u/Willem)\ **Post date:** [November 21, 2023, 10:39am UTC](https://community.naturalcapitalalliance.org/t/what-are-the-units-of-the-sdr-outputs/4274/1 "2023-11-21T10:39:51Z")
Hey all, Can somebody help me with what the units are of the outputs ‘avoided export’ and ‘avoided erosion’ in the Sediment Delivery Ratio model? I know that they represent the valuation of vegetation, but what exactly do the numbers indicate? Thanks! ---
**Author:** ![swolny](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.naturalcapitalalliance.org/swolny/32/181_2.png) [@swolny](https://community.naturalcapitalalliance.org/u/swolny)\ **Post date:** [November 21, 2023, 3:50pm UTC](https://community.naturalcapitalalliance.org/t/what-are-the-units-of-the-sdr-outputs/4274/2 "2023-11-21T15:50:53Z")
Hi @Willem, and welcome to the forum! [As noted in the InVEST User Guide](https://storage.googleapis.com/releases.naturalcapitalproject.org/invest-userguide/latest/en/sdr.html#interpreting-results), the units of avoided export and avoided erosion are tons/pixel/year. The User Guide also contains more information about these outputs in the section [Evaluating Sediment Retention Services](https://storage.googleapis.com/releases.naturalcapitalproject.org/invest-userguide/latest/en/sdr.html#evaluating-sediment-retention-services). ~ Stacie ---
**Author:** ![Willem](https://avatars.discourse-cdn.com/v4/letter/w/898d66/32.png) [@Willem](https://community.naturalcapitalalliance.org/u/Willem)\ **Post date:** [November 27, 2023, 12:59pm UTC](https://community.naturalcapitalalliance.org/t/what-are-the-units-of-the-sdr-outputs/4274/4 "2023-11-27T12:59:03Z")
Dear Swolny, Thank you for your helpful comment. Upon converting the unit of soil loss (usle) tonnes/pixel/year into tonnes/hectare/year (by dividing it by 25 since the pixels are 500x500m each), I come on an average soil loss (usle) value of around 22 ton/hectare/year. Usually, these values should barely exceed 10. Do you know what could have gone wrong? I checked: - The inputs have the right units - The inputs have realistic values - The output map shows higher avoided erosion rates in realistic/expected locations (e.g. at steep slopes). So there seems to be something wrong with the total values. Did you ever had a similar problem? I have attached the my inVEST output files in this link may that prove useful: [SDR output - Google Drive](https://drive.google.com/drive/folders/1o2VMswW4P0XOgodkGUAQ9A4X2zs9OUCZ?usp=drive_link) ---
**Author:** ![swolny](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.naturalcapitalalliance.org/swolny/32/181_2.png) [@swolny](https://community.naturalcapitalalliance.org/u/swolny)\ **Post date:** [November 27, 2023, 5:40pm UTC](https://community.naturalcapitalalliance.org/t/what-are-the-units-of-the-sdr-outputs/4274/5 "2023-11-27T17:40:37Z")
Hi @Willem - It is often the case that model results are significantly different than reality, especially with a model as simplified as SDR. We always recommend calibrating the model with real-world data before using the absolute values in any sort of decision-making context. If it’s not calibrated, we feel much more confident in the relative high-low values and spatial patterns, not so confident in absolute values. ~ Stacie ---
**Author:** ![Willem](https://avatars.discourse-cdn.com/v4/letter/w/898d66/32.png) [@Willem](https://community.naturalcapitalalliance.org/u/Willem)\ **Post date:** [November 28, 2023, 8:36am UTC](https://community.naturalcapitalalliance.org/t/what-are-the-units-of-the-sdr-outputs/4274/6 "2023-11-28T08:36:58Z")
I see, that makes sense. Thanks a lot once again 🙂 EDIT: For those interested, I solved the issue. I had to update the usle\_c values in the biophysical table, they were too high (hence, erosion rate was also too high) ---
**Author:** ![Willem](https://avatars.discourse-cdn.com/v4/letter/w/898d66/32.png) [@Willem](https://community.naturalcapitalalliance.org/u/Willem)\ **Post date:** [December 19, 2023, 8:27am UTC](https://community.naturalcapitalalliance.org/t/what-are-the-units-of-the-sdr-outputs/4274/7 "2023-12-19T08:27:20Z")
Quick question: Are avoided export and avoided erosion outputs the amount of erosion/export that vegetation _currently_ is avoiding, or is it the potential when there would be vegetation on those locations? ---
**Author:** ![swolny](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.naturalcapitalalliance.org/swolny/32/181_2.png) [@swolny](https://community.naturalcapitalalliance.org/u/swolny)\ **Post date:** [December 19, 2023, 5:15pm UTC](https://community.naturalcapitalalliance.org/t/what-are-the-units-of-the-sdr-outputs/4274/8 "2023-12-19T17:15:49Z")
The avoided erosion equation is RKLS - USLE RKLS does not include vegetation factors. USLE = RKLS plus the C and P factors, which do add the effect of the vegetation in the LULC map. So the difference between them is showing the effect of current vegetation on erosion from that pixel. ~ Stacie ---
**Author:** ![Willem](https://avatars.discourse-cdn.com/v4/letter/w/898d66/32.png) [@Willem](https://community.naturalcapitalalliance.org/u/Willem)\ **Post date:** [December 20, 2023, 8:50am UTC](https://community.naturalcapitalalliance.org/t/what-are-the-units-of-the-sdr-outputs/4274/9 "2023-12-20T08:50:01Z")
Thank you! It is interesting to see that a changed P factor has neglectable impact on the avoided erosion but has a significant impact on the avoided export. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex031/uploads/naturalcapitalproject/original/2X/8/8d95591aa074da87ea0fdd61ca47c1c3c0588aa7.png) [@system](https://community.naturalcapitalalliance.org/u/system)\ **Post date:** [March 19, 2024, 8:50am UTC](https://community.naturalcapitalalliance.org/t/what-are-the-units-of-the-sdr-outputs/4274/10 "2024-03-19T08:50:22Z")
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