You can only close tunnels after normalisering in/out traffic to/from Gaza. Now they are a life line. There is nothing in international law allowing to cut off a whole population from its normal requirements. They are now starting at the wrong side: first you should normalize traffic and after that the tunnels are not needed anyway.
5 killed, 24 injured in attacks in southeast Turkey (AP)
from the article: Hamas: Egypt destroying Gaza smuggling tunnels by flooding them