Tricks, treats and Flood Awareness Month

It's October — the spooky season when leaves crunch underfoot, jack-o'-lanterns adorn neighborhood porches and bite-sized candy bars are everywhere.

October is also Flood Awareness Month, marking the shift away from warm and dry weather to the start of fall precipitation. Rain is especially needed now to help alleviate Washington's current drought and wildfire conditions.

As our seasonal weather patterns shift, some places in Washington could experience flooding. The Department of Ecology shares how flooding typically occurs, what people can do to find their flood risks, and the potential benefits of flood insurance.

They are the lead state agency responsible for helping cities and counties identify and reduce their flood risks, comply with Washington's floodplain management laws, and maintain enrollment in the National Flood Insurance Program administered by the Federal Emergency Management Agency (FEMA).

As part of Flood Awareness Month, they are partnering with Washington state's Office of the Insurance Commissioner, Emergency Management Division, and Department of Natural Resources to share vital information.

Flooding in Washington state

Since 1970, all 39 counties have experienced at least one flood severe enough to warrant a presidential disaster declaration.

Major floods can threaten lives and livelihoods, disrupt businesses, commerce and rail lines, and close local roads, state highways and thoroughfares connecting the nation. In December 2007, the largest flood ever recorded in the Chehalis River basin in Southwest Washington closed U.S. Interstate 5 for several days and submerged large parts of the cities of Centralia and Chehalis. There were two fatalities and $900 million in damage.

Unfortunately, due to climate change, floods in Washington are expected to become bigger, more frequent, and more dangerous. Scientists warn these trends will continue as our weather patterns become more unpredictable.

Types of flooding

Floods occur naturally and can happen almost anywhere. Although river and coastal flooding are the two most common types in Washington, flooding can happen anywhere. Let's break down the different types of flooding in our state.

River flooding occurs when water in a stream or river channel accumulates faster than it can be carried away. Our rivers typically flood due to persistent thunderstorms, atmospheric rivers, ice jams and combined rainfall and snow melt. In Western Washington, river flooding usually happens after prolonged winter rains. In Eastern Washington and Cascade Mountain range, spring snow melt and rain-on-snow events are the primary culprits.

When high tides combine with heavy rainfall, strong winds and waves, and low atmospheric pressure, residents along Washington's 3,300 miles of tidal coastline can experience coastal flooding. When these conditions also coincide with a "king tide" – the highest predicted tides of the year – inland flooding can occur along Puget Sound, Strait of Juan de Fuca and the Pacific Ocean because these conditions can also push high tides up to 20 feet above predicted levels. Unfortunately, due to sea level rise, today's king tides are likely to become everyday tides in the future.

Flood risks are not just limited to areas along our rivers and coast. Surface water flooding, especially in the state's urban areas, can happen after several days of moderate rainfall or intense precipitation in a short period of time because hard surfaces such as streets, parking lots, roofs and driveways prevent rain from soaking into the soil.

After heavy rains, flash flooding can occur as raging torrents ripping through riverbeds, urban streets and mountain canyons. Flash floods are unpredictable and usually occur within minutes, but sometimes hours, after excessive rainfall. Areas scarred by wildfires are particularly susceptible to flash flooding because heavy precipitation runs off almost instantly, causing creeks and drainage areas to flood quickly and at higher-than-normal levels. Stormwater runoff can also mobilize rocks, boulders, downed trees, sediment and other debris, creating particularly dangerous conditions.

Understanding flood risks

Since anywhere it rains can also flood, every home and property in Washington has some level of flood risk. Don't be spooked, however, because there are many things you can do to be prepared.

First, it is important to know whether your home or property is in area considered at "high," "moderate" or "low" risk of flooding.

FEMA's Flood Map Service Center is the official public source for flood hazard information to support the National Flood Insurance Program. FEMA also continually updates its flood risk maps to reflect changes in land development and other factors.

Understanding the flood risk for your home or property is the first step in being flood prepared.