Puget Hazards Completed

9722-ADU - Urban Hydrologic and Geologic Hazards in Puget Sound, Washington

Problem - Current hazards programs of the USGS focus on understanding and monitoring the physical processes that result in individual natural hazards and on producing assessments of these geologic and hydrologic hazards. In the Puget Sound basin, hazards that are especially common and also have a high propensity for damage include earthquakes, floods, and high winds. This initiative will be concerned primarily with earthquakes and floods, and information on high winds will be acquired from NOAA and included in the analysis. Other hazards in the region that are discussed are either more localized, cause less damage, or are less frequent and include landslides, debris flows, tsunamis, and volcanic eruptions.

Although substantial knowledge about these natural hazards now exists and important monitoring systems are in place, implementation of mitigation measures and preparedness actions that would reduce losses have lagged. Typically, many private firms and government agencies have more advanced response plans (what to do after disaster strikes) than aggressive actions to lessen losses.

Only recently has consideration been given to the idea of characterizing regions in terms of multiple geologic and hydrologic hazards. Usually, mitigation measures are tied to individual hazards, making it difficult for many local jurisdictions and private companies to easily factor multiple-hazard loss-reduction strategies into their long-term planning. Indeed, without a proper framework and a complete understanding of possible losses, mitigation techniques for one hazard may contradict those for another. For instance, building in flood plains is discouraged to reduce potential flood losses. However, highly liquefiable ground is often found in flood plains, and engineering solutions to overcoming liquefaction rely on more intensive development on a particular site. In addition, most local jurisdictions and many private companies suffer both from poor loss estimates as well as poor methods to relate mitigation efforts to a reduction in the size of these loss estimates.

Finally, focusing on a single urban area adds new complications. As usually cast, national multiple-hazard and loss assessments are seen as the call to action for mitigating the catastrophic hazards: big earthquakes, big floods, and big windstorms. Focusing on individual urban areas will require careful integration of losses from low-frequency, high-damage hazards (such as powerful earthquakes); and higher-frequency, lower-damage hazards (such as severe flooding). The disparity in the potential costs and frequency of various natural hazard events provides a major opportunity for the USGS to test the uses of multiple-hazard statements in single urban areas.

Objectives - The overall goal of this effort is to improve the utilization of earth-science research results in support of disaster mitigation measures, disaster response, and long-term urban planning that will reduce human and economic losses from natural hazards in the five-county, Seattle/Tacoma area.

The objectives of the five-year initiative are:

• Fill identified data and knowledge gaps that limit our understanding of geologic and hydrologic hazards in the Seattle/Tacoma area.
• Involve Federal, State, local, and private stakeholders to help design useful multiple-hazard information and products.
• Translate our understanding of geologic and hydrologic processes into a clear statement of hazards.
• Develop a statement in a multiple-hazard format tailored to the urban environment of Puget Sound.
• Provide single-hazard loss analyses for the urbanized portions of the study area.
• Develop a method to perform a multiple-hazard loss assessment for the study area.
• Communicate information about multiple-hazards and losses to users and collaborators in an effort to encourage public and private mitigation and loss reduction efforts.

Relevance and Benefits - In the last decades, increasing development in areas subject to natural hazards such as earthquakes, flooding, and volcanic hazards have led to ever larger losses associated with these hazards. As a result, it is recognized that greater emphasis must be placed on loss reduction, or mitigation. Although substantial information exists about many natural hazards, and important monitoring systems are in place, implementation of mitigation measures and preparedness actions have in general lagged plans that focus on response to natural disasters. Additionally, what mitigation plans that do exist are traditionally tied to individual hazards, making it difficult to create long-term loss-reduction strategies that incorporate the breadth of potential disaster scenarios.

The Urban Geologic and Hydrologic Hazards Initiative, informally referred to as the Seattle Area Natural Hazards Project, addresses these planning needs by identifying and filling gaps in current understanding of the individual hazards, and presenting that information in an integrated manner. For example, although the Seattle area is known to be a seismic hazard zone, recent discovery that the area is subject to great earthquakes (magnitude 8 or larger) has illuminated the lack of understanding of the area's susceptibility to such earthquakes. Similarly, recent large flooding has pointed out the need to improve and quickly update flood maps as hydrologic conditions change and our understanding of flood probabilities improve. To facilitate robust long-term loss-reduction planning, the project will synthesize hazards information into an integrated hazards description intended to help planners make decisions about how to plan mitigation for areas that are subject to low-frequency, high-damage hazards such as earthquakes as well as higher-frequency, lower-damage hazards such as floods.

Approach - This project will use a coordinated interdisciplinary approach that builds on the established strengths of the participants and aggressively fills data and knowledge gaps during the first three years. We propose to fill most of these gaps using existing programs for three reasons. First, most programs already have a rich collection of collaborators, customers, and cooperators. Thus, we will use filling of data gaps as one of building interest in multiple-hazards approaches. Second, the hazards posed by crustal earthquakes and volcanic eruptions of Mount Rainier require particular focus before being incorporated into a multiple-hazards statement. The most efficient path to increasing our certainty of these hazards is through the existing programs. And third, pulling together existing datasets from cooperators into a common digital spatial database is consistant with the Framework data concept advocated by the Federal Geographic Data Committee (FGDC) and minimizes redundant efforts.