Presentation on theme: "Kevin Bacon game: Flood modeling edition David Ford Consulting Engineers, Inc. Sacramento, CA California Water & Environmental Modeling Forum Oct. 2006."— Presentation transcript:
Kevin Bacon game: Flood modeling edition David Ford Consulting Engineers, Inc. Sacramento, CA California Water & Environmental Modeling Forum Oct. 2006
Kevin Bacon game According to Wikipedia (so it must be right, huh?) The trivia game Six Degrees of Kevin Bacon is based on a variation of the concept of the small world phenomenon which states that any actor can be linked, through their film roles, to Kevin Bacon. The game requires a group of players to try to connect any film actor in history to Kevin Bacon as quickly as possible and in as few links as possible.
Here is an example, using Elvis Presley: Elvis Presley was in the movie Change of Habit (1969) with Edward Asner. Edward Asner was in the movie JFK (1991) with Kevin Bacon.
Rules of the Kevin Bacon game: Flood modeling edition Rule 1: I made up the game, so I get to make up the rules. Rule 2: Forget the movies—no Hollywood here. Rule 3: Link one flood model/study/modeler with another flood model/study/modeler with rational linkages.
Comp. Study hydrologic analyses Highly regulated stream, so fitting frequency model to gaged data not appropriate. Common design storm approach (at right) wouldn’t work. [Where do you position the rainfall in a 26,000 sq mi watershed?] Alternative approach, documented by Hickey et al. in ASCE journal, relies on gaged flows, historical patterns, composite floodplain concept. [See John Hickey for reprint.]
Comp. Study hydraulic analyses Hydraulic analyses use unsteady network model—the mother of all UNET models initially. Geometric data collected using digital terrain models and bathymetric surveys (2-ft contour lines.) Over 100 routing reaches and approximately 3,000 cross sections. Extensive use of advanced modeling features, including hydraulic storage areas, lateral weirs, flow diversions, levees, and bridges.
Yuba-Feather basin Oroville Dam New Bullards Bar Dam
Yuba-Feather operation challenges Contributing watersheds large, with much unregulated flow. Rainfall and snowmelt runoff. Travel times long. Dynamic natural + engineered system. Operations managed by several agencies.
Benefit of forecast-coordinated operation Reservoirs interconnected, so decisions felt throughout system.
Benefit of forecast-coordinated operation Reservoirs interconnected, so decisions felt throughout system. Greatest benefit when operations coordinated. For example, best use of 300 kcfs capacity at confluence considers current and future states of both reservoirs.
Relationship of Comp Study and F-CO Corps of Engineers did extensive study of hydrology and hydraulics in Central Valley for the Comprehensive (Comp) Study. 2005 DWR study used design hydrographs from Comp Study to investigate flood operation options for Oroville and New Bullards Bar reservoirs. Findings from study supported concept of F-CO project efforts; models formed foundation for work.
How should we determine the 100-yr WSEL @ Howe + Northrup? Use 100-yr design storm + 100-yr d/s boundary condition (BC) Use 100-yr design storm + ? d/s BC Use ? design storm + 100-yr d/s BC All of the above
“Coincident frequency” analysis If statistically independent, use total probability theorem Pick a stage Use eqn to get probability Pick another stage Repeat, repeat, repeat Combine to get stage-probability
Interior area elevation-frequency function (at pond)
Illustration of computation LAR (exterior) stage (ft) (1) F(32.18| LAR stage) (2) F(LAR stage) (3) F(32.18| LAR stage) * F(LAR stage) (4) 22.50.0020.540.001 270.020.220.004 310.130.140.018 360.200.100.020 sum = 0.04
Hydrology for map modernization for San Joaquin basin? Although study not yet completed, hydrology tools being developed. Can’t use typical simple river approach in lower reaches due to impact of SJ river. So what do we do?
Round 2: D05 pond and New Melones Dam Stages in channel upstream of D05 pond affected by watershed runoff AND by pond elevation, which is affected by LAR stage. Need “coincident frequency analysis” to account properly for both upstream and downstream conditions if independent. Stages at some locations in channel downstream of New Melones affected by releases and San Joaquin River flow (stage), so need coincident frequency analysis here too.
Martis Dam PMF study Joe DeVries managed PMF study (for Corps) of Martis Dam. PMF=runoff from severe combo of meteorologic + hydrologic conditions. Caused by PMP. PMP in this watershed has snowmelt.
FERC snowmelt guidelines Compute using HEC-1 energy-budget model. Requires Shortwave radiation Dewpoint temperature Temperature sequence Wind speed sequence Rainfall sequence Area covered by snow at start of storm Snowpack water equivalent Snowmelt temperature Change in temperature with elevation
Where do we get data to calibrate/ verify snowmelt model? Our hero
Round 3: Joe DeVries and David Parker Joe DeVries managed PMF study of Martis Dam for Sacramento District of Corps. Martis Dam PMF inflow includes snowmelt runoff, so snow data + snowmelt model needed. Snow data stored by CDEC. David Parker manages CDEC data dissemination system.
What’s my point? Kevin Bacon linkages are a fact in flood modeling. Flood studies often related by goals, methods, data, analysts, results. We never really finish much. Flood studies may have a long legacy, so: Do them good enough initially. Take the time to document them. Share your toys. Flood models, carefully assembled, can be re-usable and scalable.