addressing climate change adaptation in regional transportation plans

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The islands in the lower Bay-Delta are defined as those areas below mean sealevel (see Figure 8). These areas hold back water on a continuous basis and crestheights target the peak water conditions due to tidal fluctuations from the sea,peak flows from the rivers, or the combination of the two. Levee failures andsubsequent island flooding regularly occur; over 160 failures occurred in the lastcentury (DWR, 2009). Levee failures and flooding occur due to peak water levelconditions, but they can also take the form of what are called “sunny day” failuresduring which there are no adverse loading conditions.The Delta has yet to experience a substantial earthquake in its currentconfiguration. The seismic behavior of the levees in the Delta is a concern,however, because the levees have not been designed or tested for such loadingconditions and may fail via several different mechanisms (e.g., seismic liquefactionof the foundation or embankment soil, co-seismic deformation of the foundationor embankment soil, or post-seismic reconsolidation of the foundation soil). Thescenario that threatens disruption of the state’s water supply is an earthquakethat can result in multiple levee failures, flooding the freshwater into the belowsea level islands, and allowing saltwater intrusion to degrade water quality therebyshutting down water exports to the south (DWR, 2009).Because the levees in the lower Delta currently hold back water on a continuousbasis (in some places upwards of 8 meters) incremental increases in sea level orincrease in peak-flow heights will not have an appreciable impact on the seismicvulnerability. The concern is earthquake loading of the vulnerable levees, notrelatively small increases in the static loading from increased water level heights.This also holds true for any other asset or community in the lower Delta residingbelow mean sea level. Seismic levee integrity and static levee integrity are notnecessarily addressing the same failure mechanisms.The lower Delta islands are continuously dropping in elevation, below sealevel, due to a number of factors. One main factor is the loss of topsoil fromagricultural activities. An increase in average temperatures accelerating the dryingof peaty organic soils and an increase in wind storm severity could exacerbatethis process, resulting in lower island elevations, increased static levee loading,and higher levee vulnerability. Also of concern are the high water conditions anderosion that are associated with winter storms. While they might not cause thewidespread failure that may result from a seismic event, storm events have thepotential to result in a notable increase in levee failure.Changes in precipitation can have an influence on maintaining the saltwaterfront below the intake pumps for the water delivery to the south. Currently thesaltwater front is maintained primarily by controlling the release from Shasta Dam,APG: UNDERSTANDING REGIONAL CHARACTERISTICS PAGE 54
among other flood control structures. Unreliable water supply and timing fromthe input rivers (Sacramento, Mokolumne, and San Joaquin) due to changes inprecipitation and snow melt will make ensuring water quality and water deliveryincreasingly difficult.Climate Change Impacts in the Upper Bay-DeltaClimate change is expected to result in the following outcomes in the upper Bay-Delta:• Increased precipitation and snowmelt peak runoff are likely to increase thestatic vulnerability of levee.• Not have an appreciable impact on the seismic vulnerability of the levees.For communities in the upper Delta that are above mean sea level (behindlevees that are not continuously holding back water), increased peak flows dueto climate change pose a threat to the static stability of the levees but will nothave an appreciable impact on the seismic vulnerability of the levees. The odds ofcoincidence of higher peak flows with earthquake ground shaking are negligible.However, earthquake ground shaking could damage levees, and if not repaired intime, subsequent peak water levels could result in levee failures. Increase in sealevel will affect the static stability of the levees just above current mean sea leveland may provide more static push during seismic events, but again the change isinsignificant compared to the overall seismic vulnerability of the levees. Again,seismic levee integrity and static levee integrity are not necessarily addressing thesame failure mechanisms. The “Water Management” section of APG: Defining Local& Regional Impacts provides further discussion of flooding.Evaluating Climate Change ImpactsAn approach to evaluating levee vulnerability to climate change impacts is todivide adaptation needs into chronic ongoing problems and catastrophic impacts.Ongoing problems address small-scale damage and disruption such as propertydamage, crop loss, or similar effects that can usually be quantified in terms ofinsurance claims and can be addressed with maintenance. Catastrophic impactsinclude the shut-down of the state water exports, disruption of regional or stateinfrastructure (highways, rail lines, telecommunication and power grids, gas andwater mains, etc), or other broad multi-jurisdictional or dramatically disablingimpacts that often require more substantial fixes.Addressing impacts requires close collaboration between local jurisdictions andthe levee districts and other flood control or levee management entities. ForDelta communities these stakeholders are critical members of the climate changeadaptation team who can aid in supplying critical data and providing feedback inunderstanding risk.PAGE 55APG: UNDERSTANDING REGIONAL CHARACTERISTICS
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Addressing Climate Change Adaptatio
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appendix b reportState-of-the-Pract
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State-of-the-Practice Climate Chang
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C A L I F O R N I AADAPTATIONPLANNI
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Adaptation Planning Guide - Advisor
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List of Tables (cont’d.)Table 6.
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Climate Impact RegionsThe APG is or
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APGSTART HERE:PLANNING FOR ADAPTIVE
Page 198 and 199: What are the designated climate imp
Page 200 and 201: CA Climate Adaptation Planning Guid
Page 206 and 207: • Selected Demographic Data. Sele
Page 208 and 209: Cal-Adapt ProjectionsTable 1. Summa
Page 210 and 211: Selected Infrastructure and Regiona
Page 212 and 213: illnesses due to air pollution resu
Page 214 and 215: Additional Resources• Sea level r
Page 216 and 217: Cal-Adapt ProjectionsTable 5. Summa
Page 220 and 221: frequency can harm forests. Large i
Page 222 and 223: Bay Area RegionCounties: Alameda, C
Page 224 and 225: the Sacramento and San Joaquin rive
Page 226 and 227: Table 12. Selected Population Data
Page 228 and 229: Sea level rise is also expected to
Page 230 and 231: Additional Resources• Public Heal
Page 232 and 233: Cal-Adapt ProjectionsTable 13. Summ
Page 236 and 237: Table 16. Selected Population Data
Page 238 and 239: As with crops, climate change impac
Page 240 and 241: Additional Resources• Wildfire Re
Page 242 and 243: elevations, increased static levee
Page 244 and 245: The ecosystem functions of the Delt
Page 246 and 247: Setting and HistoryThe California D
Page 250 and 251: Some of the questions that should b
Page 252 and 253: Southern Central Valley RegionCount
Page 254 and 255: Biophysical CharacteristicsThe west
Page 256 and 257: The crops produced are varied and i
Page 258 and 259: Communities in this region should e
Page 264 and 265: have the resources to prepare for,
Page 266 and 267: Additional Resources• Sea Level R
Page 272 and 273: Timber practices have also had ecos
Page 274 and 275: Southeast Sierra RegionCounties: Al
Page 276 and 277: Biophysical CharacteristicsThe sout
Page 278 and 279: ultimately result in reduced water
Page 284 and 285: particular concern are populations
Page 286 and 287: Additional Resources• Sea Level R
Page 292 and 293: industry around Big Bear. As there
Page 294 and 295: California Natural Resources Agency
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addressing climate change adaptation in regional transportation plans

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