A rectangular channel is 400 ft wide and the normal depth is 10 ft with an average velocity of 5 fps. A roadway is to cross the channel using a bridge with equal encroachments from each side. Determine the water depth at Section 2 and 3 for bridge lengths (B) of 100, 150 and 200 ft. What is the maximum length of bridge that will cause critical depth to occur in the constriction? Neglect headloss and channel slope.