Squeezing the Waterways in Greater Yellowstone

Lack of protection for streamside vegetation has degraded the creek within the National Elk Refuge, where a few thousand elk spend the winter months. Their numbers have eliminated sapling cottonwoods and shrubs along Flat Creek, except for one stretch that has been protected by a fenced exclosure. The fenced-off area, vibrant with diverse deciduous shrubs and young cottonwoods, gives an indication of what Flat Creek would look like if the rest of it were similarly protected.     

Streets and buildings have been built directly adjacent to the creek, and significant investment has been made by the Flat Creek Watershed Improvement District and Teton Conservation District in an effort to prevent flooding due to ice dams in winter. But we’re trying to fix a problem that we have created instead of allowing the creek and its associated groundwater to flow naturally.

Why does this matter? For starters, we would prefer to avoid having this infrastructure, including homes and businesses, flooded. More importantly, if we don’t take steps to improve the creek’s ability to flow more naturally, the existing problems will only get worse.

In undeveloped areas, water moves into drainages systems after being slowed and absorbed by soil and vegetation. Where natural sponges in the form of soil, riparian areas, and forests are replaced by impermeable surfaces—concrete, asphalt, roofs—water can’t filter into the ground. Runoff happens more quickly, increasing the chance of the creek overflowing its banks.

When the natural stream channel is made artificially narrow by encroaching structures, riprap or fill, seasonal high water and stormwater runoff have nowhere to spread out, so water rises in the channel and backs up to inundate the area upstream.

Removing trees, shrubs and grasses from undeveloped property, along with subsequent excavation and grading, will leave the land unprotected from erosion. Weeds get a foothold. Sediment from the bare area ends up in the creek and large amounts enter Flat Creek at manmade outfalls. The town of Jackson is working to correct this problem, but these are in violation of EPA standards.

Replacement of said undeveloped land with development equates to a loss of habitat for aquatic species and the adjacent riparian areas needed by wildlife—including mammals and birds. Also lost is the parklike atmosphere of natural streams that attract people for rest and recreation. Water temperature rises as shade-providing streamside vegetation is replaced by concrete, which warms the water flowing over it.

Water quality becomes impaired from urban runoff, which is laden with sediment and typically contains fertilizers, hazardous chemicals, heavy metals and hydrocarbons from vehicles, as well as all manner of other substances that don’t belong in the creek.

Where channels have been straightened or narrowed and vegetation has been removed from the banks, streamflow velocities increase. Result: increased channel and bank erosion.

Jackson town managers and engineers are well aware of these problems. But as with all desirable mountain towns, commercial square footage is at a premium here, and newer developments are designed to maximize that potential. Moderately sized buildings that leave some open space on lots for trees, grass and shrubs are being replaced by structures that take up the entire property with concrete walkways extending from structure to curb, leaving no room for vegetation on which the eye can rest or rain can find its way into the ground.

Residential parts of town are being redeveloped in a similar way. Within a couple of blocks of my house are a dozen “For Sale” signs in front of houses once owned by neighbors I knew. Most of these houses will be torn down and the mature trees removed, to be replaced by structures twice their size. Driveways and garages tend to be wider as well, with a corresponding reduction of vegetation.

The one part of town that remains relatively natural is around Karns Meadow Park, where the creek meanders through a dense and diverse assemblage of willows, river birch and other tall shrubs. It is a jewel in the midst of development. 

While local government entities and nonprofits, including Trout Unlimited and Protect Our Waters Jackson Hole, have tried to improve conditions in and around Flat Creek, the march of construction and development continues apace, with more in the works.

Adjacent to town, agricultural land is slated to become the next large residential subdivision. A proposed mega-hotel with two levels of underground parking, to be located on the north end of town near the historic confluence of Flat Creek and its major tributary Cache Creek, is being considered by the town council. If approved as submitted, this structure will require pumping groundwater from around the basement structure to prevent hydraulic buildup against its walls. It’s not hard to imagine where the pumped water, with its potential load of fine sediments, will end up.

I wonder when we are going to seriously address the health of Flat Creek, which could be the thriving heart of Jackson, rather than continuing to degrade it. Other towns in our region are resurrecting their urban waterways, but I’m not sure that is a priority here. It’s more a matter of trying to keep an imprisoned creek from causing damage to all that we have built around it. We should learn from other urban areas that have created more risk of flooding and damage as they add to the infrastructure.