With natural streams and manmade systems, Harris County now has about 2,500 miles of channels, significantly higher than the 800 miles of natural channels that originally existed in the county. Almost all of the man-made and improved channels were built prior to establishing the criteria of the 1% (100-year) flood.
Contrary to popular belief, not many of the miles of man-made or improved channels are concrete lined. Only about 6% of the channels in the county are concrete lined - most are grass lined. All of the channels in Harris County carry stormwater runoff resulting from normal rainfall quite well. The county doesn't flood with normal type rainfall. However, under extreme rainfall conditions when rainfall exceeds several inches per hour for several hours, many areas of the county are susceptible to flooding. After all, flooding IS Harris County's natural disaster.
Nature - A Force to be Reckoned With It is a popular urban myth that, in Houston's and Harris County's past, flood plains were contained to the channel banks and that land development has caused all of the area's flooding problems. That is not true. Nature can and will provide more rainfall than the area's channel systems can handle. What we have today is a county that "drains" very well, but still "floods" a lot. So, although the belief early in the last century was that man could control nature (even the District's name implies that control is the goal), the fact is that, reducing risk is possible - eliminating risk is not. What we do is cope with the natural flooding potential in order to take advantage of everything else this region has to offer.
Expansive, Expensive Network is Part of Our Landscape Our bayous and waterways are an integral part of the local landscape. Houston is widely known as the Bayou City, and the rest of Harris County is much the same. In many places throughout the county, our bayous offer distinctive vistas, whether in their original pristine condition, or sculpted by modernization. With a $4 billion network of flood damage reduction infrastructure in the ground, the District still faces enormous tasks in the future. Balancing the use of land with its ability to store and convey floodwaters is a continual challenge in what is now the nation's third most populous county, encompassing the nation's fourth-largest city.