AN EVALUATION OF HURRICANE AGNES' FLOODS IN COMPARISON TO BRIDGE DESIGN INFORMATION AVAILABLE FOR PENNSYLVANIA CONTEMPORANEOUSLY

IN THE YEARS 1970, 1971, DESIGN MANUALS HAD BEEN ISSUED FOR STATE OF PENNSYLVANIA ON PREDICTION OF EXTREME RAINFALL AND ANTICIPATED FLOODS. ON JUNE 22, 1972, HURRICANE AGNES DUMPED UP TO 13" OF RAIN IN FIVE DAYS, PRODUCING VERY SEVERE FLOODS. THE REPORT PRESENTS THE RESULTS OF COMPARISON OF EXTREME FLOODS STATISTICALLY PREDICTED TO ACTUAL FLOODS CAUSED BY HURRICANE AGNES, WITH FOLLOWING RESULTS: 1. PREDICTIONS FOR A LARGE PART OF PENNSYLVANIA WERE VIRTUALLY UNAFFECTED. 2. AGNES PRODUCED THE MAXIMUM FLOOD PEAK IN 24 OUT OF 44 STREAMS SMALLER THAN 200 SQUARE MILES. 3. INCLUSION OF 1972 YEAR INTO ANNUAL FLOOD SERIES INCREASED THE SLOPE OF THEIR GUMBEL LINES BY AN AVERAGE OF 42%. 4. THE REGIONAL FLOOD FREQUENCY METHOD GENERALLY GAVE PREDICTIONS WHICH STILL APPEAR SATISFACTORY FOR MOST WATERSHEDS. 5. THE EXCEPTION TO 4 ABOVE APPEARS TO TO BE IN CAVERNOUS LIMESTONE WATERSHEDS, WHICH GAVE UNEXPECTEDLY HIGH RESPONSE TO AGNES. 6. ADDITIONAL EVIDENCE SUGGESTS THE INADEQUACY OF GUMBEL STRAIGHT LINE. LOG-GUMBEL MIGHT BE BETTER FOR HIGHWAY DESIGN.

  • Corporate Authors:

    Reich, Brian M, Pe

    ,    
  • Authors:
    • Reich, B M
  • Publication Date: 1973-5-14

Media Info

  • Pagination: 56 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00204056
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: Final
  • Contract Numbers: FHWA-PO-3-1-1440
  • Files: TRIS, USDOT
  • Created Date: May 24 1974 12:00AM