Near miss on flooding
The Ames–Nevada area received exceptionally heavy rainfall on Thursday morning, June 14. Thunderstorms tend to be spotty, but six to seven inch amounts were common across the area. That kind of rain in only a few hours on soil that was already well watered led to lots of rapid runoff and local flooding, but it could have been much worse. Most of the upstream watersheds, including Squaw Creek, Skunk River, and East and West Indian Creeks, received lesser amounts. A friend south of Story City measured only 3.5 inches. That’s a lot of rain, too, but had heavier amounts fallen only a few miles farther north, there would likely have been much more extensive flooding in the Ames-Nevada areas.
Floods have plagued humans at least back to Noah’s time. Human activity and land use choices tended to make floods worse through the centuries as forests were cleared and wetlands drained. Settlements tended to be built near water sources, and though our cities have spread out on adjoining uplands, many heavily developed areas are still in or near flood plains, where damage can be greatest. Technology to attempt major flood control and protection like levee systems and large dams became available only in the last century or so. Most of these efforts tended to focus on the downstream end of floods, near developed areas. All the while, increased drainage of the land on farms and in cities continued to add more water more quickly to streams and rivers that couldn’t move it away fast enough. That process continues yet today. Many rivers and streams were channelized (shortened) to speed the flow of water, but that only increased downstream flooding even more. Floods have grown progressively worse as a result. Precipitation trends have added to the problem, as large rainfall events have increased in frequency and intensity since the mid to late 1900s.
Levees prevent floodwater from spreading out on flood plains, forcing it to go elsewhere. Levees and dams, when they work, still have their place in protecting high risk areas from flooding, but they often give people a false sense of security that has encouraged them to continue developing and living in high risk areas. Much of the past century’s history involved humans trying to get rid of as much water as possible as soon as possible, and drainage efforts, for better or worse, continue to be a fact of life. In spite of our history, long-term flood control efforts need to include at least as much, if not more, work in the upper areas of watersheds if they are to be successful. More precipitation needs to stay closer to where it fell for longer periods of time. Restoring wetlands, large and small, wherever possible is a logical part of that effort. They are nature’s best water storage systems, and they also benefit humans by acting as kidneys to help remove pollutants before gently releasing cleaner water into ground water and streams. Small ponds, storm water retention basins, grassed waterways, terraces, contouring, cover crops and farm programs like CRP that encourage planting of grasses or trees all have their place in slowing, not speeding, runoff from the land. They all contribute to more and cleaner water being stored on and in the land (ground water), rather than sending it down the nearest stream as fast as possible.
Development and land-use policies need to be rethought to prepare for future flood events that are sure to come. We all have some responsibility for and stand to benefit from improved resource use and planning. Federal and state conservation programs and the public funding that supports them have often been cut, even though badly needed. They need to be strengthened to encourage better management of our water resources. Although flooding can never be totally prevented, we can and should do a much better job of managing our water resources.