Pick up the incorrect statement from the following

• Side walls of a venturi head flume are splayed out from the end of the throat at 1 : 10 for a length of 4.5 m
• Length of side walls should be such that the width of the flume is made equal to 2/3rd the bed width of the distributary
• Once the width of the flume becomes 2/3rd of the width of the distributary, the splayed walls are increased to 1 in 3 to get full bed width
• None of these.