addressing climate change adaptation in regional transportation plans

Addressing Climate Change Adaptation in Regional Transportation PlansA Guide for California MPOs and RTPAsDevelop Digital Elevation MapsDigital elevation maps provide a critical geospatial dimension lacking in mostembedded asset data – that of relative elevation. A roadway layer, for example,typically contains the extent and path of the road and, with the benefit of a widthor “lanes” field, some measure of width. However, the elevation of the roadwayabove a parallel drainage ditch is rarely known.By incorporating a separate elevation layer into the GIS, most assets will assumethe topography of the terrain beneath them. In many areas, high resolution 14laser (LiDAR) generated elevation data is obtainable, either through the U.S.Geological Survey 15 (USGS) or the NOAA Digital Coast web site. 16 Many largecities and urbanized areas have commissioned their own high resolution digitalmaps. Lower resolution (7.5-minute) maps are available nationwide through theUSGS National Map, last updated in 1992. 17An important caveat to the use of most LiDAR data is that manmade structuresare generally removed during processing. Although this has little or no effect onroadways or rail, for instance, bridges and skyways are removed, leading to adepiction of inundation for every structure crossing an existing waterway. Ifpossible, these structures should be left in during processing, although thisrequires significant foresight and processing often takes years to complete. Somestructures will have full or partial relative elevation information included in thedata. Bridge deck clearances over navigable waterways or other rights-of-way(road or rail) are usually available through NBI datasets, for example – althoughthis field is likely to be null for largeculverts and bridges crossing nonnavigablewaterways. In this case, thestatus of the bridge approaches may offerclues as to whether the bridge will berendered unusable during a flood event,but this technique generally cannot beapplied systematically (i.e., each bridgewould require visual examination by theassessment team).Climate Assessment in Just Two DaysOahuMPO conducted a two‐day workshop inMarch 2011 to discuss the climate impactsprojected to affect Hawaii. Climatescientists, planners, and engineers at thecity, state, and Federal levels attended thisevent, which focused on sea‐level rise,flooding, and increased storm frequency andintensity. Through this process, participantsidentified five specific areas as the mostvulnerable transportation assets/locationson Oahu.Source: OahuMPO (2011).14 Less than 1 meter horizontal and 10 centimeters vertically is typical.15 http://lidar.cr.usgs.gov/.16 http://www.csc.noaa.gov/digitalcoast/.17 http://nationalmap.gov/.9-12 Cambridge Systematics, Inc.