Extracted text: 15. Rigid boundary channels carrying sediment free water, should consider: a) The velocity of should not be slow for silting b) The velocity of should not be high for scouring c) The velocity is determined from Mannings formula 16. The conveyance of a channel section increases with: a) decrease in the wetted perimeter. b) increase in the wetted perimeter. c) does not depend on the wetter perimeter. 17. Flow in most sanitary and storm sewers can be treated as: a) Hydraulic flow b) Open channel flow 18. For Muskingum method, two constants values are given: Co= 0.6, C1=0.2, then which of the following will be a possible value of C2. a) 0.2 b) 0.22 c) 0.25