addressing climate change adaptation in regional transportation plans

Addressing Climate Change Adaptation in Regional Transportation PlansA Guide for California MPOs and RTPAsMore intense precipitation may cause an increased incidence of flooding alongcoastal roadways and rail lines. Low-lying bridge and tunnel entrances for railand rail transit will also be more susceptible to flooding, and thousands ofculverts and other drainage infrastructure could be undersized—designed fortoday’s precipitation instead of tomorrow’s. 7The cycle of landslides closely follows the rainfall intensity in the winter months.Repeated periods of high-intensity rainfall often result in landslides throughoutthe State, resulting in, among other things, closures of roads, rail lines, and othertransportation systems. For example, the recurrence of the La Conchita landslideroughly every 10 years is caused by winter storms that, in the last failure,completely closed Highway 101 and the parallel rail corridor for a week (CNRA2012).Changing precipitation could result in erosion and subsidence of transportationinfrastructure like rail beds, causing the interruption or disruption of traffic. Thechanging precipitation (for instance, changes from frozen to liquid precipitation)could change runoff patterns, increasing the risk of floods, landslides, slopefailures, and consequent damage to roadways and rail beds, especially ruralareas in the winter and spring months. 8Impacts of Changing Temperature on the RegionalTransportation SystemCalifornia should expect overall hotter conditions by the end of the century. Allmodel projections suggest increased temperatures, with the level of emissionsrepresenting the biggest uncertainty: temperature levels will rise more quicklyand be higher by the end of this century with higher emissions.Changes in temperature may damage materials used in roads and othertransportation infrastructure. The increase in average temperature will also havea cumulative impact on the material properties of infrastructure systems.Individual days of extreme temperatures can also produce failures. Typicalconstruction materials degrade in extreme heat, cold, and moisture. An increasein the intensity of these elements will result in more rapid degradation of analready aged infrastructure.Changing temperature may affect increased freeze-thaw conditions, creatingfrost heaves and potholes on road and bridge surfaces and compromising railbeds. Longer periods of extreme heat can cause deformation of asphalt and rails,increasing the chance of derailments, or at a minimum, requiring speed7 Ibid.8 Ibid.Cambridge Systematics, Inc. 4-9