Eagleridge Fluvial Hazard Assessment

Project Goals

• The Fountain Creek Watershed District focuses on organizing and distributing funding that it receives to improve projects and raise awareness for the health of the watershed.
  • Creates partnerships between companies and groups to organize projects such as mapping while ensuring it receives the funding to do so.
  • Attempts to bring awareness to the importance of water quality and conservation through marketing and community engagement techniques.
• In our project specifically, we are utilizing mapping of the active stream channel, through time and compared to aspects of the surrounding land, to help become aware of the fluvial processes that occur and have an impact on the surrounding communities.
  • With this information, dynamic river processes like erosion and channel avulsion can be better anticipated and the resulting hazards, such as flooding, can be predicted and mitigated.

What happens as humans develop infrastructure surrounding these dynamic systems?

Fountain creek cuts through different types of shale, alluvium, and one instance of eolian deposited sand. The shales present in this region: Kps, Kpt, and Kns, are known to be less competent than other types of rock in this region due to their many layers of bedding. Because this relatively erodible rock is the primary bedrock of this section of Fountain Creek, a layer of alluvium has formed on the creek bed as eroded rock eventually settles when the river’s transport capacity is exceeded for each individual grain size.

The Fountain Creek Watershed also has tributaries that bring sediment in from the mountains to the west, which include sources like Pikes Peak Granite, Fountain Formation and some hornblende gneiss, and eolian (loess and dust) deposits from the east. These processes have created depositional layers of alluvium along and on top of the creek valleys.

The geologic composition of Fountain Creek can have a large impact on water routing and flood hazards. The small grain sizes present in shale mean that this stream carries large amounts of suspended load. Along with this, surrounding calcareous alluvium can lead to ionic load when acidic rain is added to the system. Because most of the stratigraphy for this area is composed of shale, a weak, flakey rock, sediment flux and deposition are likely to increase with higher discharge. With high precipitation and the low permeability qualities of both shale and the soil present in such an arid region leads to flashy runoff during precipitation events that could contribute to a rapid increase in discharge within the creek.