Modeling Ballasted Tracks for Runoff Coefficient C

Details

• Creators:
  Molinas, Albert ; Mommandi, Amanullah
• Corporate Creators:
  Hydrau-Tech, Inc.
• Corporate Contributors:
  Colorado. Dept. of Transportation. Research Branch ; United States. Federal Highway Administration
• Subject/TRT Terms:
  • Rail transit
  • Light rail transit
  • Drainage
  • Runoff
  • Hydrology
  • Pollution control
  • Pollution
  • Heavy metals
  • Permits
  • Best practices
  More +
• Publication/ Report Number:
  CDOT-2012-8
• Resource Type:
  Tech Report
• Geographical Coverage:
  Ohio
• Edition:
  Final.
• Corporate Publisher:
  Colorado. DTD Applied Research and Innovation Branch
• Abstract:
  In this study, the Regional Transportation District (RTD)’s light rail tracks were modeled to determine the Rational Method ; runoff coefficient, C, values corresponding to ballasted tracks. To accomplish this, a laboratory study utilizing a ; rainfall-runoff facility was conducted at Colorado State University’s Hydraulics Laboratory. The input to this model was ; provided by using RTD’s design criteria, data from existing installations, and a field study to sample surface materials along ; ballasted tracks. By subjecting the 1:1 scale model railroad segment to 1-hour rainfall events with various recurrence ; intervals and measuring the corresponding runoff volumes, runoff coefficients were computed for Denver hydrology. For ; the more frequent 2-year, 5-year, 10-year events, the average C value is approximately 0.55. For the 25-year, 50-year, and ; 100-year return frequency rainfall events, the C value is in excess of 0.55 and is expressed in terms of multiplication factors ; of this average value. The runoff coefficient for ballasted tracks is significantly larger than the previously tabulated values ; for railroad yards. The higher runoff coefficient reflects the design of ballasted tracks to drain rainfall as quickly as possible. ; As a part of the research, detention times in the ballasted tracks were also determined. The detention time is a function of ; antecedent soil moisture content and rainfall intensity. In general terms, for dry antecedent conditions the initial 0.3 inch-0.4 ; inch of rainfall is detained in the ballasted tracks. The initial 0.5 inch of rainfall produces only a small amount of runoff. For ; 25-year, 50-year, and 100-year events, the runoff starts 9 minutes, 7 minutes, and 6 minutes after the start of the event. ; Implementation ; It is recommended that the CDOT use the newly determined C values in the CDOT Drainage Design Manual.
  More +
• Format:
  PDF
• Funding:
  107.00
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/24782/dot_24782_DS1.pdf
• File Type:
  [PDF - 1.12 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:07aea1b8ee6d47e7ad63c13bcdbd57c8200a691b71b062c0167b1641b6f844b7