Coastal Hazards: An Overview
Stretching 3,300 miles, Washington’s shorelines provide economic, environmental, and social benefits for communities throughout the state. Washington’s coastal areas are also inherently vulnerable to the dynamic nature of coastal processes, leading to coastal hazards. To learn about specific coastal hazards and how they interact, click through the buttons below.
How are these hazards related? It is important to understand how hazards can affect each other and consider these compounding effects in your plan or project. For example, erosion of a dune system may lead to flooding and salinity intrusion – damaging structures, farms, and habitats. Similarly, a tsunami may follow an earthquake, but tsunami evacuation may be hindered due to damaged roads and buildings from the earthquake.
How does climate change affect these hazards? Many hazards will increase in magnitude as climate change continues. Sea level rise is directly influenced by climate change and can increase the impacts or risk of flooding, erosion and deposition, tsunamis, landslide, and other changes. Read about individual hazards below to learn more.
How do human activities affect these hazards? Many towns and buildings in Washington have been built in low-lying, hazard-prone areas. Without adequate planning, people may continue to build in hazard-prone areas. These structures may be at risk and the infrastructure that protects them can also change the flow of water – exposing other areas to hazards. For example, riprap or bulkheads can protect shoreline properties but can also cause erosion on adjacent properties.
Coastal flooding occurs when low-lying land is covered by seawater. Multiple factors can combine to cause coastal flooding: storm surge, king tides, sea level rise, increased river flows, and tsunamis.
Riverine flooding occurs when creeks, rivers, or other waterways carry more water than their channels can accommodate. This can cause dry land to become flooded – particularly where waterways meet high tides, where historic floodplains have been developed, and where streams bend or meander.
Sea level rise is an ongoing increase in ocean water levels over long time periods (decades to centuries). The latest research in Washington provides data on projected sea level rise for all areas of the state’s coast, taking into account local variation in vertical land movement.
A tsunami is a series of waves that form from a sudden displacement of water. Tsunamis are typically caused by earthquakes offsetting the seafloor, but they can also be caused by landslides into or under water.
Coastal erosion is the loss of coastal land. It occurs when sediments and other shoreline materials are picked up and moved by water, wind, ice, or gravity. Coastal deposition is the opposite of coastal erosion; it is the creation of new landforms or topography along the shoreline after material has been eroded.
A landslide refers to the downhill movement of rock, soil or debris. The term landslide can also refer to the deposit that is created by a landslide event.
Earthquakes are sudden releases of energy that happen when rocks slide past one another along an underground crack, or fault. Earthquakes cause the ground to shake and can lead to vertical or sideways movement of the ground surface.