QA: tool to automatically find streams/rivers flowing uphill

Hi,

am I right that there is no automatic stream/river direction checker?
http://wiki.openstreetmap.org/wiki/Quality_assurance

At least in Slovakia I occasionally find some parts of rivers or streams which are marked in wrong direction - i.e. they flow uphill.

I guess it should be possible to make such a script based on some elevation dataset.

Maproulette has a fix waterway challange