Needs to Update Probable Maximum Precipitation for Determining Hydrologic Loading on Dams

Transcription

1 Needs to Update Probable Maximum Precipitation for Determining Hydrologic Loading on Dams USSD 2017 Annual Conference Anaheim, CA Chandra S. Pathak, PhD, PE, F.ASCE Engineering and Construction Branch HQ - U.S. Army Corps of Engineers April 5, 2017 US Army Corps of Engineers US Army Corps of Engineers

2 Background Probable Maximum Precipitation (PMP) is used in computing the Probable Maximum Flood (PMF). PMF is used as a design criteria for several critical infrastructure projects including: Dams/Reservoirs Nuclear Power Plants others

3 Motivation Dam Safety Program: Assessing hazards under hydrologic loading conditions Previously computed PMP and PMF are many decades old. Need to update PMP and PMF to determine revised hydrologic loading for several dams/reservoirs

4 PMP Defined Probable Maximum Precipitation (as defined in HMR 55A): Theoretically the greatest depth of precipitation for a given duration that is physically possible over a given size storm area at a particular geographic location at a certain time of the year.

5 Extreme Precipitation Recorded

6 Extreme Precipitation Recorded

7 Key PMP Manuals ( ) Current NOAA/NWS PMP Documents and Related Studies Manual on Estimation of Probable Maximum Precipitation (WMO/2009) PMP Standards Have Existed For Years Methods and Assumptions in Need of Revision

8 PMP Estimation Process

9 Missing Extreme Storms in HMRs HMR Year A Critical need to update the extreme storm database Some HMRs include zero storms from the past 45 years!!

10 Recent Extreme Storms not in HMRs Late December 1996 March 1997 Ohio Valley Late December 2005 May 2010 Nashville, TN New Insights - Extremes

11 Extreme Storm Database USACE Extreme Storm Database

12 Use of New Tool: HEC-MetVue Observed Rainfall Design Storm Should be user friendly Can quickly compare recent storms to PMP Should reduce time needed for site-specific PMP Should help in performing meteorological analysis for transpositioning Calculation of Basin Averages (PMP)

13 Challenges in Estimating PMP 1. Professional Judgment a. Several steps need decisions that would require professional judgment b. Need to have good understanding of atmospheric processes c. HMRs are dated and need recent additional storms Hayes, B. et al. (2015). Site Specific Probable Maximum Precipitation Estimates and Professional Judgment. American Geophysical Union Fall Meeting, December 18, 2015, San Francisco, CA

14 Professional Judgment Hayes, B. et al. (2015). Site Specific Probable Maximum Precipitation Estimates and Professional Judgment. American Geophysical Union Fall Meeting, December 18, 2015, San Francisco, CA Session H51P: Advances in Hydro-meteorological Extremes Forecasting: Estimation, Integrated Risk Analysis, and Applications I (Paper: H51P-02)..

15 Professional Judgment.. Identify steps in estimating PMP that require professional judgment For those steps, develop detailed guidance - i.e., sub-steps for a variety of conditions along with appropriate methodology Spell out assumptions used in the above methodology.

16 Challenges in Estimating PMP 2. Site Specific PMP Studies a. Need to include more recent storms b. Need to remove generalization c. Need detail analysis for each basin SSSSSSSS SSSSSSSSSSSSSSSS PPPPPP aaaaaaaa, dddddddddddddddd, ssssssssss tttttttt, = ff rrrrrrrrrrrr pppppppppppp,

17 Challenges in Estimating PMP 3. Estimating PMP Uncertainties a. Single point PMP estimate is it enough? b. Qualitative estimation (sensitivity analysis) c. Quantitative estimation (simulation) PMP Estimate

18 Challenges in Estimating PMP 3. Estimating PMP Uncertainties a. Single point PMP estimate is it enough? b. Qualitative estimation (sensitivity analysis) c. Quantitative estimation (simulation) PMP Estimate

19 Challenges in Estimating PMP 3. Estimating PMP Uncertainties a. Single point PMP estimate is it enough? b. Qualitative estimation (sensitivity analysis) c. Quantitative estimation (simulation) PMP Estimate

20 Challenges in Estimating PMP 3. Estimating PMP Uncertainties a. Single point PMP estimate is it enough? b. Qualitative estimation (sensitivity analysis) c. Quantitative estimation (simulation) PMP Estimate

21 Challenges in Estimating PMP 3. Estimating PMP Uncertainties a. Single point PMP estimate is it enough? b. Qualitative estimation (sensitivity analysis) c. Quantitative estimation (simulation)

22 New Method - Numerical Modeling Can we use knowledge of past events + high resolution numerical model simulations to better estimate (current and future) PMP? Explore utility of high-resolution, event-based modeling in Complex Terrain with the Weather Research and Forecasting (WRF) model Control RH 1.5x RH 100% 72-h total precipitation (mm) Moisture Maximization proof of concept, Colorado (Sankovich et al, 2012)

23 ASCE/EWRI - Task Committee New Task Committee on Use of Atmospheric Numerical Models for Estimating Probable Maximum Precipitation Sept/Oct 2014 EWRI/ASCE Surface Water Hydrology Technical Committee Committee has 15 members from Consulting, Academia, Research, and Federal agencies Committee has three year-term For details please contact: Dr. Chandra S. Pathak, chair chandra.s.pathak@usace.army.mil Dr. Li-Chuan Chen, vice-chair lichuan.chen@noaa.gov Prof. Levent Kavvas, vice-chair leventkavvas@sbcglobal.net

24 Summary/Conclusion Over-estimation from generalization = waste of taxpayer $$ Under-estimation from less severe storms = lives at risk Need site-specific PMP estimates Use Corps (in-house) developed methodology/sop Include recent extreme storm data from database Consistency in PMP Estimates Estimate uncertainties in PMP estimation

25 Questions/Comments Chandra S. Pathak, Ph.D., P.E., F.ASCE Hydrology, Hydraulics and Coastal Community of Practice (CECW-CE) US Army Corps of Engineers Headquarters Washington DC Phone: /Blackberry:

26 Subcommittee On Hydrology Purpose Improve the availability and reliability of surfacewater quantity information needed for hazard mitigation, water supply and demand management, and environmental protection. Activities Quarterly Meetings, Workgroups, Workgroup Meetings, Announcements, Conferences. Website Feb 23, 2017 SOH Quarterly Meeting 26

27 SOH Workgroups Hydrologic Frequency Analysis Work Group (HFAWG) Extreme Storm Events Work Group (ESEWG) Hydrologic Modeling Work Group (HMWG) Satellite Telemetry Interagency Work Group (STIWG) Proposed Streamflow Information Collaborative Proposed workgroup on filling data gaps Feb 23, 2017 SOH Quarterly Meeting 27

28 SOH Extreme Storm Events Workgroup (ESEWG) Thomas J. Nicholson, Chair U.S. Nuclear Regulatory Commission (USNRC) William Otero, Vice-Chair U.S. Army Corps of Engineers (USACE) Purpose and Goals: Coordinate studies and databases for reviewing and improving methodologies and data collection techniques used to develop design precipitation estimates of large storm events up to and including the Probable Maximum Precipitation (PMP). Develop a detailed scope of work/plan of study, and Determine the necessary funding requirements to update the Catalog of Extreme Storms and Hydrometeorological Reports (HMR) for estimating PMP. Feb 23, 2017 ACWI Meeting 28

29 Recommendations from Workshops and Meetings with Stakeholders 1. Coordinate Studies and Database Maintain and post active list of Extreme Storms Studies (such as PMP studies) Develop central repository for precipitation data collected by Workgroup organizations and foster data agreement with respective agencies. 2. Develop a detailed scope of work/plan of study Work with the ESEWG Proposal Writing Team (PWT) to complete detailed scope of work/plan of study 3. Determine necessary funding requirements to pursue rainfall product needs Next step is to present proposal with funding needs to SOH and then onto ACWI Focus should be on highest priority needs to include guidance and shared databases for regional and site-specific PMP estimates; and for Probabilistic Flood Hazard Assessments. Feb 23, 2017 ACWI Meeting 29