Flooding and Erosion from Climate Change, Shifting Rivers and Changing Landscapes

    By Kathleen Berger, Executive Producer for Science and Technology

    Claire Masteller, assistant professor of Earth and planetary at Washington University in St. Louis is engaged in collaborative research that will help scientists distinguish between climate-driven change and the natural variability of river channels.

    Masteller doesn’t need to go to a river during a major flood event for research, because she can create the force of floods through a flume in her laboratory. In HEC Media’s video story, Masteller sets the flow of water at 160 gallons per minute to 190 gallons of water per minute.

    “You really care about when this stuff (the gravel) starts to move,” Masteller explained. “When the gravel starts to move, you’re doing the work of erosion that’s changing the landscape.”

     Masteller is a geomorphologist.

    I like to describe geomorphology as the science of scenery,” she said. “Here in Missouri, we get a lot of rainfall in the spring. And so, we’re interested in how the floods that run through our rivers in the springtime might act to change their shape or might cause some overflows and flooding.”

     If a riverbed becomes more resistant to erosion, large rainstorms might result in more flooding, with devasting consequences. If a riverbed has severe erosion, the river will widen to accommodate bigger flood flows. Both situations spill over into social, economic, and health issues.

    “We have the erosion hazard itself. As the banks widen, you get bank collapse. If you have roads close to rivers, you can start undercutting those roads and really affect nearby infrastructure,” Masteller said. “As those banks collapse, they supply more soil and sediment into the river. That increased turbidity can affect fish habitats. Rivers are also an important source of fresh water and so water quality is linked to how often rivers erode. So, there are lots of reasons that you might want to care about a river and what it’s doing.”

     With climate change, the size and the frequency of flood events change. Masteller wants to know how rivers will respond.

    “We care about if a flood happens tomorrow, what’s going to happen to our river. Now the question is, what is the consequence of the same flood happening 10 times more frequently, 20 years from now?”

    The flume experiments are handy because scientists don’t have to wait for climate change to happen. They can study erosion patterns of varying rivers by modeling rivers big and small, from the mighty Mississippi to modest mountain streams.

    “We can change the slope of this (flume), we can change if this is a bedrock river or an alluvial river, a river that has gravel in the bottom of it. We can change the shape of that gravel. We can change how big or small the floods are. So, we can really model anything from a mountain river to a lowland river.”

    Masteller combines experimental studies of river erosion in her lab with historical flood data and geospatial data. The study of varying river channels is supported by grant of $313,872 grant from the National Science Foundation.

    “Our experiments can really help us gain some insight without having to wait for it to happen.”

    The research provides a foundation for river flood hazard forecasting models.

    “Ten-year, 20-year projections of – if this is how our weather patterns and our climate is going to change in the next 20 years, here is how our rivers might respond,” Masteller explained. “What we’re trying to do with this study is develop a method to go to a real river somewhere and say – given climate change projections, given if this river is in the mountains or if it’s in a low-lying floodplain, if there’s snow around or not, how might this river respond to climate change? How sensitive is this river versus a river sitting somewhere else?”