Neighborhood hazard evacuation bottlenecks

The structure of urban regions evolves with population growth and development, but in doing so inherent risks and dangers emerge. This is especially true in the wildland urban interface where it is not uncommon to find significant clusters of homes with limited egress, where people are forced to exit (or enter) through a restricted number of access roads. Limited points of entry/exit are bottlenecks that may create congestion, but also amplify risk and vulnerability during an hazard event, such as fire, flood, toxic release, severe weather, volcanic eruption, tsunamis, landslide, debris flow, sink hole, unexploded ordnance, improvised explosive devices, or other emergencies when evacuation is necessary. If bottlenecks are obstructed or otherwise inoperable, then neighborhood clearing is hampered. The paper introduces spatial analytics combined with geographic information systems that support assessment and planning efforts associated with hazards that may necessitate evacuation. An assessment of coastal communities in Santa Barbara County, California, is reported to demonstrate current capabilities in identifying neighborhoods that are potentially difficult to vacate and their associated bottleneck street segments that limit egress. The paper outlines future research needs to better support safety and security efforts as well as legal mandates in the assessment and mitigation of evacuation risk and vulnerability.