What is Khurra in civil engineering works?

Khurra is the a depressed place just before the outlet of rain water pipe. The water flowing from the roof moves towards khurra and flush out from the roof through rain water pipe. This is generally 45cm x 45cm in size. It is constructed as under:-

1. First one 400 micron thick PVC sheet of 100cm x 100cm size is laid over the roof slab.

2. Then 50mm average thick 1:2:4 mix cement concrete is laid over the PVC sheet.

3.The top is finished with 12mm thick cement plaster of mix 1:3 and a coat of neat cement, rounded edges and adding waterproofing compound.