Hydrologic Issues for Dams - Association of State Dam Safety Officials

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Educate Modelers to what the model doesGarbage in Groovy out - Apparent VeracityExpress confidence, sensitivity, fuzzinessUse new technology and methods2d, 3d, hydraulic routingGIS coverages for soils, vegetation, elev, slope...Combine HECRAS and HECHMSGet out of the box and see how nature worksPaper 7 – Lindon 32
State of GeorgiaFEMA Workshop on Hydrologic ResearchNeeds for Dam Safety AnalysisHydrologic Practices in the State of Georgia andother states east of the Mississippi RiverByFrancis E. Fiegle II, P. E. 1The Georgia Safe Dams Act regulates high hazard dams that are either 25 feet tall orstore more than 100 acre-feet of water at maximum pool. These regulated dams areevaluated to determine if they have adequate spillway capacity and wave action freeboardat maximum design pool to pass the design storm as defined by the Georgia Safe DamsAct (A ct) and Rules for Dam Safety (Rules). The spillway capacity is prescribed in theAct based on the height of the dam and/or its maximum storage capacity.1) Small dams - Those dams with a storage capacity not exceeding 500 acre-feet anda height not exceeding 25 feet - 25 percent PMP spillway design capacity.2) Medium dams - Those dams with a storage capacity exceeding 500 acre-feet butnot exceeding 1000 acre-feet or a height exceeding 25 feet but not exceeding 35feet - 33 percent PMP spillway design capacity.3) Large dams - Those dams with a storage capacity exceeding 1000 acre-feet butnot exceeding 50,000 acre-feet or a height exceeding 35 feet but not exceeding100 feet - 50 percent PMP spillway design capacity.4) Very large dams - Those dams with a storage capacity exceeding 50,000 acre-feetor a height exceeding 100 feet - 100 percent PMP spillway design capacity.Typically, the Georgia Safe Dams Program develops Visual Inspection Reportswhich are a streamed lined version of the old USACOE Phase I reports that were done inthe late 1970's and early 1980's for state dam safety programs across the United States.In that report, our Program evaluates the spillway capacity of existing dams with respectto compliance with the Act and Rules. Except in rare instances, the hydrology evaluationuses the NRCS/SCS Curve Number, Lag Time methodology. Of note, because thespillway capacity requirements are set forth in the Act, and the design storm is restrictedto the 6-hour PMP, the Program requires the use of Antecedent Moisture Condition IIIfor the evaluation of spillway capacity. This dramatically affects the Curve Numbersused. W e use HMR 51/52 to develop the design storm. The spillway rating curves aredone using standard hydraulic practice accounting for weir, orifice, and full pipe flow forprincip al spillway pipes/open channel flow in earth emergency spillways, etc. This1 Program Manager - Georgia Safe Dams Program33Paper 8 - Fiegle
Page 1 and 2: The National DamSafety ProgramResea
Page 3 and 4: collaboration and expertise, and th
Page 5 and 6: TABLE OF CONTENTSPage #FOREWORD....
Page 7 and 8: NEW DEVELOPMENTS AND NEEDS IN SITE-
Page 9 and 10: FOREWORDThe Federal Emergency Manag
Page 11 and 12: The PMF represents an estimated upp
Page 13 and 14: RESEARCH AREASResearch needs were b
Page 15 and 16: Lack of Historical Data for Extreme
Page 17 and 18: should be developed that will allow
Page 19 and 20: • Storms used in HMR 55A and in t
Page 21 and 22: last 20,000 year s in submitting th
Page 23 and 24: d. USBR Guidelines Publication, Dam
Page 25 and 26: was severe. There was a potential,
Page 27 and 28: Thirdly, we must develop better way
Page 29 and 30: For most projects, the first step f
Page 31 and 32: Instead of lumping the loss rates t
Page 33 and 34: adjust the rating curve for when th
Page 35 and 36: In response to this situation, TVA
Page 37 and 38: TVA established a Regional Resource
Page 39 and 40: The Utah Hydrological ExperienceByM
Page 41 and 42: The Utah Hydrological ExperienceByM
Page 43: Late SpringRain on snow eventModel
Page 47 and 48: a. HEC1• DOS based program - glit
Page 49 and 50: Long te rm hydrologic needs include
Page 51 and 52: Current State and County PracticesA
Page 53 and 54: present standards and, as such, are
Page 55 and 56: Research Needs in Dam Safety Analys
Page 57 and 58: Looking at the four test cases give
Page 59 and 60: Hydrologic Analyses Related to Dam
Page 61 and 62: (iii) Modified Expected Cost Approa
Page 63 and 64: Parameter Estimation Based on Joint
Page 65 and 66: estimation of lag times and loss ra
Page 67 and 68: Hydrology for Dam Safety - Private
Page 69 and 70: Probable Maximum PrecipitationAll o
Page 71 and 72: The most common synthetic methods a
Page 73 and 74: the standard would be very conserva
Page 75 and 76: 65Paper 12 - Cecilio
Page 81 and 82: REFERENCES1. U. S. Army Corps of En
Page 83 and 84: Overview of Flood Estimation Proced
Page 85 and 86: Extreme FloodsExtreme floods, the t
Page 87 and 88: Temporal patterns used to distribut
Page 89 and 90: Preliminary Estimates of Rainfall a
Page 91 and 92: 24 to 72 hours). CRC Research Repor
Page 93 and 94: CURRENT AND FUTURE HYDROLOGIC RESEA
Page 95 and 96:
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
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supporting sub-processes. Therefore
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Probability ofFailure P f1Probabili
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Since any rigorous analysis is an i
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well, and usually do include subjec
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Against this background, there is n
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Howson, Colin., and Peter. Urbach.
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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
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mountain watersheds in response to
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18. Schaefer MG, Stochastic Modelin
Page 127 and 128:
dams which could be used to save li
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Hydrodynamic modelMIKE 21 BACKGROUN
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A FRAMEWORK FOR CHARACTERIZATION OF
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c) Decision Level Risk Assessment:
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credible estimates of extreme flood
Page 137 and 138:
Fitting a distribution to data sets
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unoff volumes. Examples of this typ
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used to estimate frequency distribu
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Hosking, J.R.M., and J.R. Wallis, 1
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in west central Arizona. The draina
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Trial and error reservoir routings
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Figure 1 Alamo DamAlamo Dam and Spi
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Paper 19 - Chieh and Evelyn 146
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esources are made to mitigate flood
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implementing a risk-assessment meth
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Typically, the elevation of the top
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similar to that of the high-gradien
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and provides a cost-effective frame
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10000E. Colorado
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10000x Peak Discharge95% confidence
Page 167 and 168:
An integrated science approach will
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ReferencesBaker, V.R., Kochel, R.C.
Page 171 and 172:
Partnerships, Proceeding of the 200
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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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