You might want to exclude waterway=tidal_channel as well, since they’re bidirectional.
Edit: Also spotted a waterway=put_in at Way: Beach/Kayak launch ramp (355814424) | OpenStreetMap, undocumented but another good candidate for exclusion.
As the role of Spillways at the bottom of a dam is to regulate water release and some times avoid seismic reaction, let’s be reassured that water dont go up. look at usage=spillway | Tags | OpenStreetMap Taginfo or at the seismic type version James Bay Project - Wikipedia 
As we discussed in a previous thread, the difficulty with canal derivations is to determine their flow characteristic.
- they come back in the same watershed → they move down
- they can be redirected to an other watershed → they move down
- canals using the up tidal flow can move water up to saltponds
This is simply a temporary exception. I expect that globally more water is going down then going up otherwise their would be flooding aside the river. Floodings arise but are exceptional. This is why we see floodgates in places like Venetia and Rotterdam. 
There’s a large loop near me that is caused by a way using this proposal for waterway=riverbed.
May need exclusion… may need to get the proposal refined. What do we think?
It also seems that the wiki documentation for waterway=rapids could use an update to indicate that it’s not the current preferred way to tag rapids as areas (natural=water + water=rapids?). I’m happy to make the adjustment but wanted to see if that’s incorrect/controversial.
it means canoe=put_in?
they can be flowing water, but also may be not flowing one
arguably a drain without flow is not draining, or could it?
Seems that’s a more popular tag. I’m not judging the validity of the tagging, though, just saying that a closed way tagged with waterway=put_in is a false positive for a looped waterway detector.
(If we were talking tagging, I’d say that using a vehicle type as a key is already pretty overloaded, encoding both vehicle-specific access and details of transit stops. Generally, vehicle keys aren’t used for “top-level” tags to map physical features. Not saying that waterway=put_in is better, but I understand why a mapper might prefer not to use canoe=put_in, tag popularity notwithstanding.)
Ran into another candidate for the exclusion list, waterway=derelict_canal. Again, possible to “fix” this by revising the tagging but it’s not IMO an error.
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About 2000 of these are from the CanVec waterway imports having water rapids areas marked as waterway=rapids + area=yes. The wiki suggests natural=water + water=rapids for such features and seems like a sensible and easy update. I’ll talk to the folks working on those things and see about doing a mass update.
Done those 2.
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The rapids areas from CanVec have been updated to the modern tagging. 
I have spoken to the couple of folks who have recently been doing CanVec imports and they should be in a spot now where more won’t make it into the DB.
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The few hundred cases of waterway=wash (from NHD imports) have been reviewed and modified to natural=wash. It’s an unusual feature unless you’re familiar with arid climates but is described pretty well here. The surface is pretty distinct from say natural=sand or natural=rock. Anyhow, they shouldn’t trouble the loop map any more.
In my area, water is rarely flowing throughout the year. Therefore, intermittent streams and rivers are often converted into canal/ditch/drain in order to regulate their flood flow near residential areas and roads. They are certainly part of the intermittent water flow network.
If anyone would like to get stats updates from the loops data feed. I have stood up this mastodon bot:
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Interesting. Having spent a lot of time in CO/UT/AZ/NM, I’m familiar with wash’s/gullies/arroyos/gulches. Most of these in the western US are tagged as waterway=stream & intermittent or ephemeral=yes. It looks like these wash’s that were imported are all or mostly all areas and they are adjacent to an intermittent or ephemeral stream. I took a quick look at some of these and some seem wrong, and many are inconsistent.
I think wash is a new tag isn’t it? Do we need a new tag for this? natural=gully is in the wiki & used now.
natural=water, intermittent=yes could be used also.
We have natural=water, intermittent=yes for a lot of nhd imported dry ponds.
Sorry to come in so late, but I didn’t notice this until now.
Oh you’re totally fine. My guess at the “intent” (so much as there is with larger old imports) is to mark off the rough area of the intermittent/ephemeral waterway. This is why I went with something from natural=… akin to natural=river that we have for areas of persistent waterways.
I’m perfectly happy to modify it to something that better fits, or to do away with them all together. I only did a cursory glance at aerials to try and see what would be incrementally better than marking them as waterway=.
Definitely feel free to change them, suggest things for me to change them to etc.
In general, I think the waterway and water tagging for arid climates is pretty underdeveloped so I don’t mind a bit of ATYL… but it’s also totally possible I have missed a really obvious pattern folks have used.
I found several that are like this, more of a sandbar next to the river than a wash:
46228224
I think there may be many that are junk.
I’m going to be off the grid for a few days, but I’ll take a look when I get back. 
It wouldn’t bother me if someone just nukes them all.
The more I look at this, it seems that natural=* is pretty loose, probly fine to leave the ones that are wash alone.
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I’m in no rush either way. They will be here when you return. Maybe you or someone else will have an epiphany and save us all the headache! 
There’s actually a bigger problem here. The features that @watmildon retagged were generally classified using the NHD Feature Code 48400, which applies to both dry washes and bars (i.e. sand or shingle) within the courses of perennial rivers. I guess if you’re a geologist, the two are somewhat similar, since both are coarse alluvium.
You can see many of these features with their original import tags here: overpass turbo. Sadly, these features have not been well mapped in OSM. The river bars can be tagged as natural=sand or natural=shingle depending on their composition. Using natural=shoal + surface=sand/gravel/shingle is also acceptable.
But we don’t have a great tagging scheme for dry washes. That’s a subject for a more detailed discussion, so I’ve started a new thread: Properly mapping dry washes
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Fun stuff, a stream pool with three outlets. A trifurcation!
