Greater Flood Risk
Warming temperatures cause snows to melt earlier in the spring and allow storm systems to generate more rain (warm air holds more moisture than cold air). As a result, seasonal floods are expected to arrive earlier in the spring, and the risk of catastrophic floods is expected to increase.
Spring Floods are Coming Earlier
Because spring is arriving earlier, snow packs are also melting earlier. This means that many streams and rivers are reaching their peak flows earlier in the season. This, in turn, affects the availability of spawning habitats for some fish species. The earlier arrival of spring floods may also contribute to worsening drought by mid-summer, stressing vegetation and wildlife, and increasing the risk of wildfire events.
Intense Storms and Altered Weather Patterns Increase Flood Risk
Because rainfall is expected to come less frequently, and via more intense storms, floods are likely to become more common and extreme. Precipitation in the United States increased by 7% over the course of the past century, and is expected to increase even more in the coming decades. Most notable is that fact that the strongest 1% of rain storms increased by nearly 20% over the past decade.
How Do Changes in Past Flood Patterns Affect Natural Resources and Conservation Priorities?
The consequences of earlier and more frequent floods include:
- Potential loss of important spawning or nursery habitat for certain fishes, amphibians and other water- or wetland-dependent species
- Increased risk of drought, due to the earlier timing of spring floods and the longer duration of summer.
- Worsening erosion, and increased runoff of topsoil and agricultural chemicals.
- Loss of crops or livestock to floods.