Hydrology 201 for Dam Safety
Recorded on March 13, 2012 (120 minutes)

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The Hydrology 201 Webinar consists of four one-half hour segments.  The first segment is a brief review of Hydrology 101 emphasizing some of the important hydrologic issues.  The second segment will concentrate on the NRCS procedures to determine the loss rate function and the dimensionless unit hydrograph as it is utilized to transform excess rainfall into runoff.  Different methods of determining time of concentration and lag time will be covered in this session.  The third segment will be a brief introduction to the US Army Corps of Engineers Hydrologic Center’s computer model HEC-HMS and the last segment will be an application of the NRCS procedures to a small watershed utilizing the HEC-HMS model. 

Dr. Miller is a nationally-recognized expert in hydrology, hydraulic engineering, and dam safety.  He is a Distinguished Professor Emeritus of Civil and Environmental Engineering at Penn State University, where he was the head of the Water Resources Group prior to joining AECOM in 2006 as a a Science Practice Leader.  He has over 40 years of experience in water resources performing research, consulting and publishing in hydrology, hydraulics, floodplain delineation, dam safety, bridge scour, river mechanics and sediment transport. 

Dr. Miller served as Chair of the Energy Power Research Institute (EPRI) Task Committee on Standards for PMP for Dam Safety Analysis, he served on the Task Committee of ASCE that established their National Guidelines for the Hydrologic Safety of Dams and served as Chair of a Task Committee for FERC that established their Federal Guidelines for Dam Safety, he co-authored their chapter on hydrologic computations dealing with reservoir analysis. 

In 2007 he was awarded the ASDSO Hampton Medal for outstanding contributions to research and practice in hydrologic and hydraulic engineering for dams. 

Hydrology 201
Topic Outline


  1. Review
    1. Hydrologic Cycle 
    2. Gauged Watersheds
      1. Flood Frequency Analysis
        1. Bulletin 17B
        2. Uncertainty Analysis
      2. Unit Hydrograph Theory
        1. Sherman 
    3. Ungauged Watersheds
      1. USGS Regression Equations
        1. Uncertainty 
      2. Synthetic Unit Hydrograph Theory
        1. Snyder’s Synthetic Unit Hydrograph
        2. Clark’s Instantaneous Unit Hydrograph
        3. NRCS Dimensionless Unit Hydrograph
  2. NRCS Dimensionless Unit Hydrograph Theory
    1. Runoff Curve Number
    2. Timing Parameters
      1. Time of Concentration
      2. Lag Time
      3. Time to Peak 
      4. Base time
    3. Mokus’ Lag Time Relationship
    4. Partial Area/Variable Source Concepts
  3. Computer Modeling with HEC-HMS
    1. Introduction to HEC-HMS
      1. Project Organization
      2. Main Components
      3. Modeling Elements
  4. Example of Small Watershed Application