Abstract
In case of taking water out of rivers, we must realize the character of rivers. Since Dr. Kinoshita discovered ‘Sarekitai’(Alternating sand bar or Transverse bar in English) originally, the research on the relation between river bed forms and flood flows has made the rapid progress in Japan. But in the field of agricultural engineering, his research is not yet adopted sufficiently.
Reinvestigating diversion weirs from this point of view, the formation of Sarekitai, we can find out a nice technique.That is a curved oblique weir.Modern weirs are built making a right angle with river channels, but·old ones, mostly constructed during the 17 th or 18 th century, crossed rivers obliquely and curvedly.
The author discovered the following advantages of those curved oblique weirs through the fieldwork and his experimental studies.(1) Safety of weirs against flood flows.(2) Easy construction.(3) Deep digging does not occur in the downstream of the weirs.(4) Safety of intake gates.(5) Small change in the form of river bed after construction.
Thus the author clarified the rationality of curved oblique weirs, especially against flood flows, on the basis of the conception of ‘Sarekekitai’
