If you live near a waterway, chances are you will face the natural rise and fall of the water level in that waterway.

Flooding is a natural stream process. A floodplain is the land that is inundated with water during floods. This area allows flood waters to spread out and slow down, reducing their erosive force. When a stream is able to naturally expand into its floodplain, it rejuvenates the ecosystem by replenishing nutrients and recharging aquifers. However, many of the streams in Multnomah County have lost their connection to their floodplain by being confined into ditches and culverts. When this happens, property damaging flood events are often the result, and houses and buildings in the floodplain fall victim. The “perfect storm” of spring snow melt and marine storm systems moving across our region can cause water levels to rise quickly. Flow changes can also be driven by alterations in type and density of vegetation, roads, and buildings as well as in soil infiltration rates (how quickly water can seep into the ground). These changes can affect the magnitude, duration, and impact of floods.

So what does it mean? Maintaining floodplain connectivity and a healthy riparian area can drastically reduce chances of sustaining damage from a flood event. Building above the floodplain will greatly reduce flood damage to structures. Preserving wetlands can also reduce flood damage.