Hydrologic Issues for Dams - Association of State Dam Safety Officials

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References:1. Ad Hoc Interagency Committee on Dam Safety, Federal Coordinating Council forScience, Engineering and Technology, “Federal Guidelines for Dam Safety,” June 1979.2. U.S. Weather Bureau, “Probable Maximum and TVA Precipitation Over theTennessee River Basin Above Chattanooga,” Hydrometeorological Report No. 41, 1965.3. National Oceanic and Atmospheric Administration, “Meteorological Criteria forExtreme Floods for Four Basins in the Tennessee and Cumberland River Watersheds,”Hydrometeorological Report No. 47, 1973.4. National Weather Service, “Probable Maximum and TVA Precipitation Estimateswith Area l Distribution for Tennessee River Drainages Less than 3000 Square Miles inArea,” Hydrometeorological Report No. 56, October 1986.25Paper 6 – Lowe, Hughes
The Utah Hydrological ExperienceByMatthew C. Lindon, P.E. 1The Utah Dam Safety Section is fairly deterministic in requiring the PMF to berouted by all High Hazard dams. Incremental damage assessments can be used to reducethe design flood, especially for debris basins and smaller flood control structures. TheHMR – 49 Local storm PMP that is required for the PMF calculations has been revised toaccommodate a state specific areal reduction developed by Dr Don Jensen at Utah StateUniversity. In the event that the 6-hour local storm PMP is less than the general storm,72-hour PMP, the general storm becomes the design event, with its lower peaks, largervolume and longer runoff characteristics.Problems that we have encountered in design storm calculations include the lackof rain and flow gages that make statistical analysis and calibration difficult, if notimpossible. Our typical calculation involves black box solutions such as synthetic unithydrographs, curve numbers or constant infiltration rates. We need more physicallybased runoff models tied to soil types, vegetation, spatial and temporal precipitationdistributions, probably in a GIS type format with hydraulic, finite element, geographicalrouting. We need calibrated models that give accurate results as well as effectivegraphics.An example of long-term spillway outflows is the typical spring-time snow meltevent in many of Utah’s high mountain dams. Drainage basins typically produce asmuch as 33 cfs per square mile in continual runoff, sometimes for weeks at a time. Rainon snow events can compound these flows and if the spillway is clogged with snow andice, the dam can eventually overtop and fail, as was postulated for the failure of the TrialLake dam in 1985 (although the failure was officially deemed an act of God).Another hydrologic modeling example was our experience with the Quail CreekDike failure. After completing all the modeling classes given by HEC and the NWS weexperienced a large dam failure and subsequent flood. When we tried to simulate thebreach and the flood with our models we had a difficult time recreating the reality thathad been observed. Breach size, timing, piping initiation and breach migration weredifficult to reproduce. Routing required huge Manning numbers to simulate roughnessand we had difficulty accurately portraying the observed hydraulic jumps, attenuation andtiming of the flood wave. If we had such a hard time modeling a flood we experiencedfirst hand, how could we have faith in our models of hypothetical floods?Again, we need to have physically based models that can be calibrated and tied toreality. We need improved methods that take advantage of new technology such as 2dand 3d models, hydraulic routing, GIS, and NEXRAD radar, to match the apparentveracity of the amazing graphics and animations of the input and output. We need to1 Utah DNR, Dam Safety Hydrologist27Paper 7 – Lindon
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: TVA established a Regional Resource
Page 41 and 42: The Utah Hydrological ExperienceByM
Page 43 and 44: Late SpringRain on snow eventModel
Page 45 and 46: State of GeorgiaFEMA Workshop on Hy
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
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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
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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
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Currently transposition limits for
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pro cedures are used to allow the h
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Use of Atmospheric Models in Rainfa
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mountain watersheds in response to
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18. Schaefer MG, Stochastic Modelin
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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
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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
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An integrated science approach will
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ReferencesBaker, V.R., Kochel, R.C.
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Partnerships, Proceeding of the 200
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Flood HydrographThe flood hydrograp
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A variety of data including informa
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Improved Flood Frequency Extrapolat
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RESEARCH NEEDS SUMMARYJerry Webb, H
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o Unsteady flow computer models for
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• Upd ate “Generalized Snowmelt
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DISCUSSION1. Genera l - After the p
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participant was asked to pick what
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RISK ANALYSIS100Relative Comparison
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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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