Diverting water in Madeira

A damming plate hanging on a wall beside a stream in Funchal

WHEN WE WERE IN the Western Cape of South Africa,  I  noticed
streams running alongside roads in rural farming areas. Occasional small channels
led off from them and into the fields of farms. At each junction of the main stream
and a side channel, there were small plates that could be used  to temporarily dam the main stream to divert water
into the channel leading to the fields.  

We are staying in Funchal, Madeira. Our guesthouse is high above
the city centre and the seafront on a road that leads down an extremely steep hill.  On one side of the road there is a fast flowing
stream. Every now and then, there are metal plates that can be inserted into
slots on both sides of this stream to divert water into the property beside the
water. This is just like what I saw in rural South Africa. Perhaps I should not
be surprised by the similarity of the damming system, but I cannot recall having
noticed it anywhere else I have visited.