This blog post was written while I was a fellow at the Institute for the Built Environment (IBE) at Colorado State University. The original post can be found here.
Many people consider rivers in urban areas to be dirty, dangerous, and polluted. Unfortunately, they aren’t always wrong. Urban rivers are convenient dumping grounds for waste, and can flood, threatening homes and businesses. However, it doesn’t have to be this way.
This blog post was written while I was a part of the CSU School of Global Environmental Sustainability (SOGES) Sustainability Leadership Fellows Program. Original posting here.
I grew up on an urban river – the White River that flows through Indianapolis. Indiana isn’t a state known for its natural beauty, and not without reason. We have no mountains or oceans, and just a sliver of a Great Lake. Like many places in the Midwest, we are more defined by our farm fields than our natural features.
This fall, one hurricane after another battered the U.S. – Harvey in Texas, Irma in Florida, and Maria in Puerto Rico. In addition to the damage from wind and storm surge, heavy rainfall from these storms caused significant flooding. Photographs provided stark visuals of just how extensive this flooding was, but it is also important to quantify their impact. Last year, Dr. Brooke Anderson and I developed an R package – countyfloods – to analyze flood magnitude using data from stream gages maintained by the US Geological Survey (USGS)1.
The storm was short and intense but the sky stayed gray long after the rain stopped. Walking outside, I saw little waterfalls cascading down the previously dry gullies that dotted the landscape. The stream – which hours before had been a grassy depression – was filling with water, turning what was a dry creek bed into a full, free-flowing stream.
This was last July at my in-laws in eastern Colorado. In this semi-arid region (dry, but not quite a desert) all but the largest rivers are empty most of the time, waiting for the next storm to send water tumbling down their channels.
Close your eyes and imagine a river. You are probably picturing a single channel, snaking across the landscape. While many streams follow this general form, it is unclear if this is the result of natural or human-driven processes. Research by Walter and Merritts1 presents an entirely new notion: that many small streams in the eastern U.S. follow this common form because of a history of human development. In actuality, these streams should have multiple small channels, crisscrossing within a valley wetland.
How do rivers keep flowing even when it is not raining? Where is that water coming from? California recently suffered from a severe drought (although that has changed lately) but most of their rivers didn’t just dry up. These streams kept flowing because of groundwater. Groundwater acts like a battery. It gets charged when it rains and then slowly releases that water into streams and rivers, providing a continuous “power” source.
Rivers change. They are, by their very nature, dynamic systems which are constantly adjusting to efficiently carry the load of water and sediment they receive. Of course, not all rivers exhibit the same degree of dynamism. Steep streams with abundant sediment are much more mobile than lowland streams. One very visible way that this inherent tendency for change manifests itself is in river planform, that is the view of the river from above.
As we grow older, our childhood perceptions are challenged. Growing up on a river in Indiana, I thought it was a pristine example of natural beauty. I’ve later learned about just how large of an impact humans have had on this stream. A downstream dam slows the flow, creating a thick layer of muck on the stream bed. Years of excessive fertilizer and pesticide use upstream has led to significantly impaired water quality.
Sediment shapes rivers and rivers constantly move sediment to the sea.