Interior Drainage Channels
I don't know why a channel drain was used but I suspect that the contractor that installed the system used that method to keep any wall seepage from getting onto the floor.
Sawdust will cause problems with the system. By its very nature it will cake up and cause dams in the system. It will also shorten the life of your pump.
I would not cut off acces to the system in any permanent way, but it would be okay to tape over it or lay some linoluem scraps over it to keep out debris.
If you have anyone that can break some metal strips into a "U" shape that you can insert or take out at will would be the optimum answer.
Hope this helps,