I remember this incident way in 2016 - talking to a banana vendor in a country souk we actually discussed this event as I'dseen the local TV news and read web news sites mentioning flooding there and the road being cut.
He assured me he'd just made the trip and the road was re-opened as he'd just come up it after visiting family.
From my logs, this conversation was on the 18-24th November 2016, so it was likely repaired fast and it's a day or two's travel for him to get to where I was (Gnidef, north side of Adrar l-Kest range)
Here's a still pics "video" of the actual event - the causeway bridge being built - posted 17th November 2016, just to prove how fast they can get main supply routes open again:
http://www.youtube.com/watch?v=-VQHFsGWYLw
I realise it's 2+ years later, but what I'm trying to say is that they can be pretty quick at temporary repairs, or at least bulldozing rocks/boulder off the road.
Washed away bridges take longer, often years to properly rebuild, but the usual plan on smaller routes is to wait for the water to go and then bulldoze a piste across the dry/damp wadi bottom. In this case, it seems they laid a causeway over the water with drainage pipes underneath while there was still water flow.
Sometimes the bridges are closed only due to the danger of it being washed away, or if the water was over-topping the roadbed of it.
Often it's just one hollow pier of a bridge that gets damaged and they can dump rubble and hardcore into the pier to re-open it quite fast - there's a good vid somewhere on Youtube of this happening to the bridge at Zagora a few years ago.
The Arabic word for flood is "fayadan" - in French it's "innondation" - handy to know.
For planning purposes, or to scare/inform yourself , search Youtube for the following phrase, adding name of nearby towns or regions you are visiting
https://www.youtube.com/results?search_query=fayadan+maroc
then, to the top left above the list of result (on a PC/web page, at least) click FILTER and select "last month" to check for recent damage and to get a clue about recent problems - at least it gives an idea if the pistes are going to be rough.
swim safe