# A question about SDR: sed\_retention, usle, sed\_export

**URL:** <https://community.naturalcapitalalliance.org/t/a-question-about-sdr-sed-retention-usle-sed-export/729>\
**Category:** Science, Research & Data\
**Tags:** sdr\
**Created:** [January 4, 2020, 4:01am UTC](https://community.naturalcapitalalliance.org/t/a-question-about-sdr-sed-retention-usle-sed-export/729 "2020-01-04T04:01:29Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![MPY](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@MPY](https://community.naturalcapitalalliance.org/u/MPY)\
**Post date:** [January 4, 2020, 4:01am UTC](https://community.naturalcapitalalliance.org/t/a-question-about-sdr-sed-retention-usle-sed-export/729/1 "2020-01-04T04:01:29Z")

</div>

Dear users and developers,  
I wonder if you can help me answering a simple question about the SDR Model.I wonder how to use sed\_retention, usle and sed\_export to calculate soil retention?Because I see different claims in the literature.  
Thanks in advance for your answers.

---

<div class="post-metadata">

**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:** [January 6, 2020, 9:14pm UTC](https://community.naturalcapitalalliance.org/t/a-question-about-sdr-sed-retention-usle-sed-export/729/2 "2020-01-06T21:14:37Z")

</div>

Hi @MPY -

Have you read the section of the User Guide called [Evaluating Sediment Retention Services](http://releases.naturalcapitalproject.org/invest-userguide/latest/sdr.html#evaluating-sediment-retention-services)? It explains that sed\_retention is an index based on changing the land use to bare ground, and it does not quantify retention from upslope. It also talks about evaluating the retention service more robustly by comparing sed\_export between the baseline condition and a scenario. The difference in sed\_export shows how much more/less erosion is retained by the scenario landscape, relative to the baseline.

If you’re looking at the watershed or sub-watershed scale, you can look at the ratio between sed\_export and USLE in the watersheds output shapefile to see what percentage of erosion is being retained in the watershed.

~ Stacie