Hydrologic Issues for Dams - Association of State Dam Safety Officials

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e. A practical approach to uncertainty analysis to enable better (more meaningful)evaluations than sensitivity analysis.Specific research items were also identified:a. Case studies of observed extreme flood events as compared with PMF and discharge andvolume frequency estimatesb. Reconstitution of rainfall-runoff relationships for extreme eventsa. Antecedent precipitation and soil moistureb. Unit hydrograph characteristics (efficiency of runoff or time of concentrationfindings)c. Compilation of paleo-hydrologic information nationwide and integration with PMF &discharge-frequency estimates; generalize findings if possible.ConclusionWe need hydrologic tools that enable advancing from strictly deterministic (design flood)evaluations to performing risk based (probabilistic) dam safety assessments.References1. Alamo Dam Risk Assessment Study, Los Angeles District Corps of Engineers, July 1999.2. Alamo Dam, Supplemental Reconnaissance Report on Inadequate Spillway Capacity at AlamoDam on the Bill Williams River, Los Angeles District Corps of Engineers, July 1993.3. Colorado River Basin, Hoover Dam, Review of Flood Control Regulation, Corps of Engineers,Los Angeles District and Bureau of Reclamation, Lower Colorado Region, July 1982.143Paper 19 – Chieh and Evelyn
Figure 1 Alamo DamAlamo Dam and SpillwayDrainage area = 4,770 square milesDam embankment height = 283 feetReservoir storage at spillway crest = 1 million acre-feetReserv oir storage at TOD = 1.3 million acre-feetExisting spillway capacity = 41,500 cfsPMF inflow = 820,000 cfs and 1.39 million acre-feetPMF overtops existing dam by 20 feetThreshold Flood = 83% of PMFPMF Peak OutflowWith dam failure = 2.9 million cfsWithout dam failure = 362,000 cfsPaper 19 – Chieh and Evelyn 144
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The National DamSafety ProgramResea
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collaboration and expertise, and th
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TABLE OF CONTENTSPage #FOREWORD....
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NEW DEVELOPMENTS AND NEEDS IN SITE-
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FOREWORDThe Federal Emergency Manag
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The PMF represents an estimated upp
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RESEARCH AREASResearch needs were b
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Lack of Historical Data for Extreme
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should be developed that will allow
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• Storms used in HMR 55A and in t
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last 20,000 year s in submitting th
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d. USBR Guidelines Publication, Dam
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was severe. There was a potential,
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Thirdly, we must develop better way
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For most projects, the first step f
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Instead of lumping the loss rates t
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adjust the rating curve for when th
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In response to this situation, TVA
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TVA established a Regional Resource
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The Utah Hydrological ExperienceByM
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The Utah Hydrological ExperienceByM
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Late SpringRain on snow eventModel
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State of GeorgiaFEMA Workshop on Hy
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a. HEC1• DOS based program - glit
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Long te rm hydrologic needs include
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Current State and County PracticesA
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present standards and, as such, are
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Research Needs in Dam Safety Analys
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Looking at the four test cases give
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Hydrologic Analyses Related to Dam
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(iii) Modified Expected Cost Approa
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Parameter Estimation Based on Joint
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estimation of lag times and loss ra
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Hydrology for Dam Safety - Private
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Probable Maximum PrecipitationAll o
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The most common synthetic methods a
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the standard would be very conserva
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65Paper 12 - Cecilio
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REFERENCES1. U. S. Army Corps of En
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Overview of Flood Estimation Proced
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Extreme FloodsExtreme floods, the t
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Temporal patterns used to distribut
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Preliminary Estimates of Rainfall a
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24 to 72 hours). CRC Research Repor
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CURRENT AND FUTURE HYDROLOGIC RESEA
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ecause existing procedures are inad
Page 97 and 98: REGULATORY INVOLVEMENT AND COMMUNIC
Page 99 and 100: Decision BasisThe third feature of
Page 101 and 102: However, should it be revealed that
Page 103 and 104: supporting sub-processes. Therefore
Page 105 and 106: Probability ofFailure P f1Probabili
Page 107 and 108: Since any rigorous analysis is an i
Page 109 and 110: well, and usually do include subjec
Page 111 and 112: Against this background, there is n
Page 113 and 114: Howson, Colin., and Peter. Urbach.
Page 115 and 116: Procedures and Analysis Technologie
Page 117 and 118: Currently transposition limits for
Page 119 and 120: pro cedures are used to allow the h
Page 121 and 122: Use of Atmospheric Models in Rainfa
Page 123 and 124: mountain watersheds in response to
Page 125 and 126: 18. Schaefer MG, Stochastic Modelin
Page 127 and 128: dams which could be used to save li
Page 129 and 130: Hydrodynamic modelMIKE 21 BACKGROUN
Page 131 and 132: A FRAMEWORK FOR CHARACTERIZATION OF
Page 133 and 134: c) Decision Level Risk Assessment:
Page 135 and 136: credible estimates of extreme flood
Page 137 and 138: Fitting a distribution to data sets
Page 139 and 140: unoff volumes. Examples of this typ
Page 141 and 142: used to estimate frequency distribu
Page 143 and 144: Hosking, J.R.M., and J.R. Wallis, 1
Page 145 and 146: in west central Arizona. The draina
Page 147: Trial and error reservoir routings
Page 151 and 152: Paper 19 - Chieh and Evelyn 146
Page 153 and 154: esources are made to mitigate flood
Page 155 and 156: implementing a risk-assessment meth
Page 157 and 158: Typically, the elevation of the top
Page 159 and 160: similar to that of the high-gradien
Page 161 and 162: and provides a cost-effective frame
Page 163 and 164: 10000E. Colorado
Page 165 and 166: 10000x Peak Discharge95% confidence
Page 167 and 168: An integrated science approach will
Page 169 and 170: ReferencesBaker, V.R., Kochel, R.C.
Page 171 and 172: Partnerships, Proceeding of the 200
Page 173 and 174: Flood HydrographThe flood hydrograp
Page 175 and 176: A variety of data including informa
Page 177 and 178: Improved Flood Frequency Extrapolat
Page 179 and 180: RESEARCH NEEDS SUMMARYJerry Webb, H
Page 181 and 182: o Unsteady flow computer models for
Page 183 and 184: • Upd ate “Generalized Snowmelt
Page 185 and 186: DISCUSSION1. Genera l - After the p
Page 187 and 188: participant was asked to pick what
Page 189 and 190: RISK ANALYSIS100Relative Comparison
Page 191 and 192: WORKSHOPONHYDROLGIC RESEARCH NEEDSF
Page 193: JOE SKUPIENPrincipal Hydraulic Engi
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Hydrologic Issues for Dams - Association of State Dam Safety Officials

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