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:
  Best Practices Denver Hydrology Detention Times Drainage Heavy Metals Hydrology Light Rail Light Rail Transit Permits Pollution Pollution Control Rail Transit Rainfall-runoff Models Rational Method Runoff Stormwater Management

  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.
  
  
• Format:
  PDF
• Funding:
  107.00
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:07aea1b8ee6d47e7ad63c13bcdbd57c8200a691b71b062c0167b1641b6f844b7
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/24782/dot_24782_DS1.pdf
• File Type:
  [PDF - 1.12 MB ]