The results of testing an experimental model are presented about the optimal dimensions of gratings on drainage inlets that are installed in triangular channels, both grassed and paved, along highways. Each channel was on a grade of either 0.5%, 2%, or 4%. Each grating was a half-scale model of the prototype. The capacity of each grating was obtained by actual measurement. The width of each grating, 36 in. for the prototype in a paved channel and 48 in. in a grassed channel, was held constant throughout the tests whereas the length of grating ranged from 18 in. to 48 in. The tests showed that, with an increase in length of the inlet, the capacity increased; the increase depends also upon the grade of the channel, the swale slope, and the back slope. In a grassed channel equal side slopes carry more water than unequal side slopes; both at slopes of 6:1 are superior to both at 12:1; and a flat grade enables more water to enter a grating than a steep grade. A good modulus of the capacity of an inlet is that flow rate of which 98% enters into the inlet and 2% bypasses the inlet. /FHWA/

  • Supplemental Notes:
    • Prepared in cooperation with the Department of Transportation, Federal Highway Administration.
  • Corporate Authors:

    Lehigh University

    Fritz Engineering Laboratory
    Bethlehem, PA  United States  18015
  • Authors:
    • Brune, A W
    • Spear, A D
    • Loush, K C
  • Publication Date: 1978-4

Media Info

  • Pagination: p. 102

Subject/Index Terms

Filing Info

  • Accession Number: 00190061
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: FHWA-PA-78-2 Final Rpt.
  • Contract Numbers: PA-RP-74-2
  • Files: TRIS, USDOT
  • Created Date: May 26 1979 12:00AM