Research Report KTC-00-18/SPR-178-98 KENTUCKY TRANSPORTATION CENTER College of Engineering REVISION OF THE RAINFALL INTENSITY DURATION CURVES FOR THE COMMONWEALTH OF KENTUCKY Our Mission We provide services to the transportation community through research, technology transfer and education. We create and participate in partnerships to promote safe and effective transportation systems. We Value... Teamwork -- Listening and Communicating, Along with Courtesy and Respect for Others Honesty and Ethical Behavior Delivering the Highest Quality Products and Services Continuous Improvement in All That We Do For more information or a complete publication list, contact us KENTUCKY TRANSPORTATION CENTER 176 Raymond Building University of Kentucky Lexington, Kentucky 40506-0281 (859) 257-4513 (859) 257-1815 (FAX) 1-800-432-0719 www.ktc.uky.edu [email protected] The University of Kentucky is an Equal Opportunity Organization Research Report KTC-00-18 REVISION OF THE RAINFALL-INTENSITY DURATION CURVES FOR THE COMMONWEALTH OF KENTUCKY By Bernadette S. Dupont Transportation Engineer II and David L. Allen Transportation Engineer V Kentucky Transportation Center College of Engineering University of Kentucky Lexington, Kentucky In cooperation with Kentucky Transportation Cabinet Commonwealth of Kentucky and The Federal Highway Administration U.S. Department of Transportation The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies o f the University of Kentucky, or the Kentucky Transportation Cabinet. The inclusion of manufacturer names and trade names is for identification purposes, and is not to be considered an endorsement. March 2000 1 1. Report No. 2. Government 3. Recipient’s Catalog No. KTC-00-18 Accession No. 4. Title and Subtitle 5. Report Date Revision of the Rainfall Intensity Duration Curves for June, 1999 the Commonwealth of Kentucky 6. Performing Organization Code 7. Author(s): 8. Performing Organization Bernadette Dupont and David Allen Report No. KTC-00-18 9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) Kentucky Transportation Center College of Engineering 11. Contract or Grant No. University of Kentucky KYSPR 98-178 Lexington, KY 40506-0043 12. Sponsoring Agency Name and Address 13. Type of Report and Kentucky Transportation Cabinet Period Covered State Office Building Final Frankfort, KY 40622 14. Sponsoring Agency Code 15. Supplementary Notes Prepared in cooperation with the Federal Highway Administration, U.S. Department of Transportation. Study Title: Revision of the Rainfall Intensity Duration Curves for the Commonwealth of Kentucky. 16. Abstract The purpose of this study was to revise and update the existing Rainfall Intensity- Duration-Frequency (IDF) Curves for the Commonwealth of Kentucky. The nine curves that currently govern Kentucky are based on data from First-Order Weather Stations in and around Kentucky. However, the new curves only utilize data from within the State. The data was gathered from both First Order and Co-operative Weather Stations. In accordance with Bulletin 71, the new curves reflect the climatological zones located within the state, thus producing only four IDF curves. 17. Key Words 18. Distribution Rainfall-Intensity-Duration-Frequency (IDF) Curves, Statement Climatological Areas, Bulletin 71, Theissan Polygons Unlimited with the approval of the Kentucky Transportation Cabinet 19. Security Classif. (of 20. Security Classif. (of 21. No. of 22. Price this report) this page) Pages 2 TABLE OF CONTENTS EXECUTIVE SUMMARY ........................................................................................iii 1. INTRODUCTION...................................................................................................... 1 1.1 Background............................................................................................... 2 2. DETERMINE AREAS OF INFLUENCE................................................................ 3 2.1 Thiessen Polygons .................................................................................... 3 2.2 Climatological Areas ................................................................................ 8 3. DATA COLLECTION.............................................................................................. 13 4. DATA ANALYSIS.................................................................................................... 14 5. DEVELOPMENT OF RAINFALL INTENSITY DURATION FREQUENCY CURVES......................................................................................... 15 5.1 Gumbel Theory of Distribution.............................................................. 15 5.2 Resulting Curves.................................................................................... 20 5.2.1 First Set of Curves – First Order Stations Only.......................... 20 5.2.2 Second Set of Curves – Similar Climatological Areas ................ 30 6. FINAL RESULTS.................................................................................................... 35 6.1 Linear Regression .................................................................................. 35 6.2 Bluegrass Climatological Area Results................................................. 37 6.3 Central Climatological Area Results .................................................... 39 6.4 Eastern Area Results............................................................................. 41 6.5 Western Area Results............................................................................ 43 7. SUMMARY .............................................................................................................. 45 REFERENCES ........................................................................................................ 46 i LIST OF FIGURES Figure 1: 1968 Rainfall Intensity-Duration-Frequency Curve for Louisville, Ky...... 1 Figure 2: Thiessen Polygons used to Determine Areas of Influence in 1968............. 7 Figure 3: Thiessen Polygons used to Determine Areas of Influence in 1985............. 7 Figure 4: Thiessen Polygons used to Determine Areas of Influence in 1998............. 8 Figure 5: Climatological Areas Within Kentucky ........................................................ 9 Figure 6: Rainfall Distribution Map shows Midwest Climatological Areas.............. 10 Figure 7: Physiographic Map of Kentucky ............................................................... 11 Figure 8: Climatological Areas of Influence Superimposed on Physiographic Map of Kentucky........................................................................................ 11 Figure 9: IDF Curve for Bristol Area......................................................................... 21 Figure 10: IDF Curve for Cairo Area......................................................................... 22 Figure 11: IDF Curve for Cincinnati Area................................................................. 23 Figure 12: IDF Curve for Evansville Area................................................................. 24 Figure 13: IDF Curve for Huntington Area............................................................... 25 Figure 14: IDF Curve for Knoxville Area .................................................................. 26 Figure 15: IDF Curve for Lexington Area ................................................................. 27 Figure 16: IDF Curve for Louisville Area.................................................................. 28 Figure 17: IDF Curve for Nashville Area .................................................................. 29 Figure 18: IDF Curve for Bluegrass Area.................................................................. 31 Figure 19: IDF Curve for Central Area ..................................................................... 32 Figure 20: IDF Curve for Eastern Area..................................................................... 33 Figure 21: IDF Curve for Western Area .................................................................... 34 Figure 22: IDF Curves for the Bluegrass Climatological Area after Linear Regression ................................................................................................. 38 Figure 23: IDF Curves for the Central Climatological Area after Linear Regression ................................................................................................. 40 Figure 24: IDF Curves for the Eastern Climatological Area after Linear Regression ................................................................................................. 42 Figure 25: IDF Curves for the Western Climatological Area after Linear Regression ................................................................................................. 44 i LIST OF TABLES Table 1: Locations of First Order Weather Stations ................................................... 5 Table 2: Counties within Thiessen Polygons............................................................... 6 Table 3: Counties within Climatological Areas of Influence....................................... 9 Table 4: Values for Reduced Variate, y, and the Corresponding Return Periods.... 17 Table 5: Values of K for the Extreme-Value Distribution......................................... 18 Table 6: Values for Reduced Mean, yn, Reduced Standard Deviation, σn, Corresponding to Various Return periods ..................................................