438. Water Rows at 18 m3/s in a trapezoidal chanel with a bottom width of 5 m and side slopes of 2.1 (H: V). The depth of flow in the channel is 2 m. If a bridge pier of width 50 cm is placed in the middle of the channel. What is " the depth of flow adjacent to the pier? What is the maximum width of a pier that will not cause a rise in the water surface upstream of the pier