Rainfall and Dam Safety-From PMP to the 100-Year Storm
Recorded on October 13, 2015 (120 minutes)

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Understanding how extreme storms and their precipitation are analyzed is critically important for dam design and dam safety.  This webinar will detail the background of PMP and storm analysis starting with the earliest work completed by the US Weather Bureau (now National Weather Service) and continuing through current statewide and site-specific PMP work.  Data and methods used to quantify rainfall spatially, temporally, and in magnitude will be discussed.  Information on how these data are applied to create return frequencies of rainfall data and the limitations of such values will be discussed.  Details on recent advances, such as the use of NEXRAD weather radar and GIS, will be discussed in relation to storm analysis and PMP development, and comparison will be provided against legacy documents such as Technical Paper 40, NOAA Atlas 2, and NOAA Atlas 14.

Specific storm examples, which are important for dam safety design, will be discussed in detail.  This will include information about the reliability of the original rainfall analyses and how that affects dam design and safety.  Information related to the storms and their relationship to both return frequencies and climate change will be provided.

The intent of this webinar is to provide non-meteorologist, hydrologist, engineers, and others involved in dam safety and design an understanding on the background of storm analysis, how they are used in PMP development, and how those data are used for precipitation frequency analysis.  The attendee should come away with an understanding of the uncertainty and sensitivity involved in the PMP process, which will allow the users to apply the data and make more informed decisions both in the design of structures reliant on rainfall information and regulators to make more informed decisions regarding dam safety.


Bill D. Kappel, Applied Weather Associates, LLC

Mr. Kappel is President and Chief Meteorologist of Applied Weather Associates (AWA) in Monument, Colorado.  Mr. Kappel received an AA from Skagit Valley College in 1992, a BS in Physical Science from Mesa State College (now Colorado Mesa University) in 1998 and a Broadcast Meteorology degree from Mississippi State University in 2001.  He served as an on-air meteorologist for 10 years at various television stations across the country prior to joining AWA in 2003.   The focus of activity at AWA has been Probable Maximum Precipitation and extreme storm analysis.  Mr. Kappel has been the project manager for several PMP studies while working extensively in the development, analysis, and publication of the PMP values.  

Douglas M. Hultstrand, Applied Weather Associates, LLC

Mr. Hultstrand is a Senior Hydrometeorologist at Applied Weather Associates, where he has been involved in all aspects of site-specific Probable Maximum Precipitation development, storm analyses, and forensic meteorological investigations.  Mr. Hultstrand received a Bachelor's Degree from the University of Colorado at Boulder (CU) (Physical Geography, and Hydrology Certificate), a Master of Science degree from Colorado State University (CSU) (Watershed Science), and is currently pursuing a Doctorate degree in Earth Sciences at Colorado State University (CSU). Mr. Hultstrand has worked with U.S. Geological Survey (USGS) Alpine Hydrology Research Group (AHRG), the Institute of Arctic and Alpine Research (INSTAAR), and the U.S. Forest Service Rocky Mountain Research Station (RMRS). Mr. Hultstrand has a passion for scale and spatial variability in precipitation processes as related to hydrology and hydrometeorology. His research and expertise are in modeling the spatial variability in snowpack processes and rainfall as function of terrain parameters and atmospheric energy to better understand and model hydrologic regimes.



  1. Background of PMP and rainfall analysis
    1. History of PMP development-timeline
      1. Where data came from
      2. How developed
      3. Where we are today
        1. Better rainfall analysis
        2. Better understanding of rainfall spatial-temporal-magnitude-NEXRAD
    2. First rainfall records and rainfall analysis
      1. Sources of data, history of analysis
      2. How collected
      3. Old storms-Catskill 1819
    3. TP-40
    4. NOAA Atlas 2
    5. Areal reductions factors
      1. Site-specific development
    6. Temporal distributions
      1. Storm based
    7. NOAA Atlas 14
  2. Q&A
  3. Site-specific and Statewide PMP analyses
    1. Replacing the HMRs
    2. Implementation of data
      1. How the PMP values are used to implement/derive PMF
        1. Challenges
        2. Lessons Learned
    3. Current progress
  4. Background of extreme/world record events/amount and intensity
    1. Smethport 1942
    2. Holt 1947
    3. Camille 1969
    4. Madison County, VA 1995
    5. Hurricane Irene 2011
    6. June 2013
    7. September 2013
    8. Islip 2014
  5. How storms are analyzed and used for developing PMP
  6. Q&A
  7. Probability of PMP and other events
    1. Example of probability development for PMP
      1. From the 100-yr to PMP
    2. Uncertainty 
      1. Probability development
      2. PMP development
      3. Micovic, et al. 2015 Journal of Hydrology paper
  8. Climate change and PMP
    1. Current practice
    2. What will happen
  9. Dam safety and PMP
    1. Hazard creep
    2. Infrastructure/rehabilitation costs
    3. Reclaimed opportunity for storage/use
    4. Safety
  10. PMP and Rainfall Analysis
    1. What's happening now
    2. What's next 
  11. Q&A