Washington

In the area you have selected (Washington) river flood hazard is classified as high based on modeled flood information currently available to this tool. This means that potentially damaging and life-threatening river floods are expected to occur at least once in the next 10 years. Project planning decisions, project design, and construction methods must take into account the level of river flood hazard. Surface flood hazard in urban and rural areas is not included in this hazard classification, and may also be possible in this location. Please see 'Urban Flood' for consideration of urban surface and river flooding.The following is a list of recommendations that could be followed in different phases of the project to help reduce the risk to your project. Please note that these recommendations are generic and not project-specific.

Climate change impacts: In western, central and eastern continental US, medium confidence in an increase in the number of extreme rainfall events. In northeast US, medium confidence in an increase in days of intense precipitation. In southeastern US, model projections are inconsistent in changes in rainfall. In Alaska, high confidence in an increase in days of intense precipitation and the number of extreme rainfall events. The present hazard level may increase in the future due to the effects of climate change. It would be prudent to design projects in this area to be robust to river flood hazard in the long-term.

Recommendations

  • LOCATION ASSESSMENT: The high-level information available in this tool may indicate the presence of river flood hazard in your project area. Before committing significant resources to this issue, a study of the surrounding landscape can help you assess whether more detailed assessment and/or intervention should be considered. More information
  • EXISTING INFORMATION: The high-level information available in this tool may indicate the presence of flood hazard in your project area. However, because flood hazard can change dramatically over short distances, the exact geographical location of your project should be checked against pre-existing flood hazard information. More information
  • TECHNICAL EXPERTISE: Consultation with flood risk experts will provide a more detailed understanding of the risk posed to your asset by flooding. The level of guidance required will depend upon the level of hazard present, the vulnerability of the asset and local legislation that might apply. More information
  • PROJECT LOCATION: Consider relocation of the project. If local flood risk information confirms your project is exposed to a high level of flood hazard, relocation to areas not prone to flooding is recommended where viable. This decision will need to be undertaken with the consideration of other hazards. More information
  • EARLY WARNING SYSTEMS: Identify early warning systems (EWS) that may exist in your project area. Receive warning messages and be aware of what happens when a warning is triggered. Ensure that the warnings will be received in the facilities built and the people working or living there. Flood early warning systems are designed to provide communities with advanced warning of an imminent flood event based on weather forecasts, rainfall and upstream water levels, and can be used to trigger deployment of portable flood defences or evacuation to mitigate impacts of a flood. More information
  • INTERDEPENDENCY: Consider vulnerability of other assets within the project's dependency network. If your project is interdependent with other projects, it is important to assess the vulnerability of the entire network if the service provided is critical. More information
  • FLOOD HAZARD MANAGEMENT: Your project or development should consider flood management measures, such as restoration of natural wetlands, removal of impermeable surfaces, or implementation of flood defences at the project site and in the upstream catchment. More information
  • DO NOT INCREASE HAZARD: Built infrastructure may alter flood hazard. Constructing a significant piece of infrastructure can significantly alter the landscape and potentially influence how an area responds during a flood. Any alteration of the landscape should be undertaken with consideration as to how this will influence the local hydrology. More information
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