Hey Gray,
looks good to me! Approved!
Regarding the rills, it makes most sense to have them around where the small streams start, such as the one in the center here: https://puu.sh/ArxXk/0ab5c010c1.png
See the diagram here for an example: https://willalvesart.files.wordpress.com/2011/02/fig5-211.jpg
I recommend just making a small little diorama first and seeing if you can get them to look good in Minecraft before incorporating them fully into your plans.
looks good to me! Approved!
Regarding the rills, it makes most sense to have them around where the small streams start, such as the one in the center here: https://puu.sh/ArxXk/0ab5c010c1.png
See the diagram here for an example: https://willalvesart.files.wordpress.com/2011/02/fig5-211.jpg
I recommend just making a small little diorama first and seeing if you can get them to look good in Minecraft before incorporating them fully into your plans.