From The Fountain Creek Watershed and Greenway District (Bill Banks) via The Colorado Springs Gazette:
If you catch glimpses of Fountain Creek while driving, biking or walking along the creek, you know it tends to be relatively inactive. You might notice cloudy water due to suspended sediment, or you might spot new underwater sandbars. Most likely, you won’t see major changes. But guess what? Fountain Creek is always changing.
Every year, Laura Hempel PhD and a team of USGS scientists investigate how our creek is changing. Dr. Hempel is a hydrologist with the U.S. Geological Survey’s Colorado Water Science Center, located in Pueblo. She explains that fluvial geomorphology is the study of how rivers shape the landscape — and are shaped by the landscape. This broad definition includes the concepts of hydrology (where the water is, how it gets there, where it’s going) and sedimentation transport. It also encompasses ecology, since vegetation influences how rivers behave.
The USGS began monitoring the geomorphology of Fountain Creek in 2012, and Dr. Hempel joined the team in 2018. Currently, the team measures elevation and elevation change in 10 study areas annually, between January and April. This “leaf-off” season improves the GPS signals. (GPS enables the team to identify exact locations.) Plus, the low flow rate during winter makes it easier to wade in and collect data in the wetted channel. This annual monitoring effort is conducted in cooperation with Colorado Springs Utilities.
In the past, the team used manual survey methods — a time-intensive “boots on the ground” approach. Covering the nearly 400 acres was a monumental effort! This year, the team will begin using LiDAR, an aerial-based mapping technology. “We can collect orders of magnitude more data points with LiDAR,” Dr. Hempel says. “Those data will allow us to produce much higher-resolution maps, which is really exciting.”
In addition to measuring elevation and elevation change, annual monitoring of Fountain Creek’s topography will allow the team to study a variety of geomorphic metrics in the future. “For example, examining changes in the streambed’s elevation can indicate whether a reach is aggrading due to sedimentation or degrading due to erosion,” Dr. Hempel notes. “We also have the ability to measure the width and depth of the active stream channel and document specific changes in geomorphology. For example, is the channel cross-section smooth and U-shaped or is it complex and braided? Is the channel migrating laterally or straightening? These are some examples of metrics we can measure from this long-term monitoring data to quantify the river’s changing geomorphology.”
Why monitor the geomorphology of Fountain Creek?
Dr. Hempel explains that measuring changes in river geomorphology can lead to understanding WHY a change is happening. Specifically, what is causing the change? “Here’s the tricky thing,” she notes. “Rivers are dynamic. For example, river meandering is a natural process. Rivers are constantly evolving, so it’s difficult to disentangle natural geomorphic change and evolution from change that is outside of the river’s natural variability. Taking a step back even further, long-term monitoring tells us whether observed geomorphic changes are — or are not — outside of the river’s natural variability.”
What might indicate an anomalous change from natural variability? “The long-term dataset can give us clues,” Dr. Hempel explains, adding a hypothetical example. “Let’s say that in the historic past, a particular meander bend grew at a rate of ½ foot per year, but for the last 10 years that same meander bend grew at a rate of five feet per year. This could indicate a fundamental change in the behavior of the river. The long-term datasets are incredibly important to document the baseline condition and, subsequently, determine whether a river has changed in a way that is outside of its natural variability.”
Active monitoring gives us an understanding of the long-term picture, particularly when a river’s behavior impacts us. “If a river is migrating laterally at a faster rate and this reduces a farmer’s acreage or threatens I-25, that’s a problem,” Dr. Hempel notes. “Managers in the basin could address this one-off problem by installing riprap, for example, but that might not resolve the long-term issue. By identifying the cause, the long-term issue becomes solvable. That’s why monitoring Fountain Creek’s geomorphology is so important.”
An engaged and informed public is a vital piece of the puzzle
Dr. Hempel encourages residents of Fountain Creek watershed to learn more about our creek. “A river reflects all the changes upstream of it,” she says. “Hydrologists call it the ‘pour point.’ Our creek literally integrates everything that is happening upstream: water, erosion, sediment and people. It’s possible that Fountain Creek can be a healthy, ‘well-behaved’ river. Or it’s possible that it won’t be healthy and well-behaved. When we have an informed public, with their voice and votes, residents can better understand our creek. They can say what they want Fountain Creek to be and, if needed, support and implement measures to improve it.”
Check out interactive maps of Fountain Creek!
If a picture’s worth a thousand words, an interactive map may be worth 10 times more. Take a few minutes to review a brief report titled “Elevation and Elevation-Change Maps of Fountain Creek, Southeastern Colorado, 2015-19,” authored by Dr. Hempel. And don’t miss the 10 interactive maps that accompany the report, illustrating elevation changes for each of the 10 Fountain Creek study areas.
For example, Study Area 1’s map layers show that the meander bend in this reach migrated toward the west and became more exaggerated between 2015 and 2019. Click the elevation-change map button, and you’ll notice that its lateral migration resulted in deposition (an increase in elevation) on the east side of the main channel and erosion (a decrease in elevation) on the west side.
To access the maps’ interactive layers, you’ll need to download the PDF files and view them in Adobe Acrobat DC — or use Adobe Reader DC, which is free to download. Find the report and maps here: http://pubs.er.usgs.gov/publication/sim3456.
Bill Banks is the executive director of the Fountain Creek Watershed Flood Control and Greenway District. The District was established in 2009, to manage, administer and fund capital improvements necessary to maintain critical infrastructure and improve the watershed for the benefit of everyone in the Fountain Creek watershed.