Sandoval Fluvial Hazard Mapping

The Fountain Creek Watershed District’s responsibility is to manage its funding (provided by Colorado Springs Utilities) to offset impacts created by the development of the Southern Delivery System (carried out by Colorado Springs Utilities), carrying Arkansas River water from the Pueblo Reservoir to the cities of Colorado Springs and Fountain, as well as to the Pueblo West and Security Water districts.

The FCWD's goals include:

• Secure sustainable funding through grants, partnerships, and other opportunities.
• Build infrastructure to scale operations if funding is received.
• Streamline projects that benefit municipalities and organizations within the watershed.
• Foster regional collaboration on watershed issues.
• Increase brand recognition through stronger marketing and advocacy.
• Promote conservation and water quality protection through community partnerships.

The FCWD's priorities include:

• Secure sustainable and supplemental funding for waterway conservation.
• Strengthen regional collaboration and position the FCWD as a hub for watershed conservation.
• Increase name recognition and raise awareness about watershed challenges through communications, partnerships, and public events.
• Foster a culture of conservation and promote the recreational value of the region’s natural spaces.

In the Sandoval Focus Area, the FCWD's project goals and priorities include:

• Channel realignment
• Floodplain reconnection
• Wetland restoration

From 1937 to 2009 the river valley margin and meander belt corridor became much narrower. The meander centerline—the line connecting the inflection points between meander bends—migrated simultaneously with the narrowing of the river valley margin and meander belt corridor. In 1937 the river was multi-threaded (almost braided), in 1957 the river was nearly straight and single-channel, and by 2009 the river was single-channel and meandering. Between 1937 and 1957, urbanization overtook both sides of the river valley, and the river meander became very straight. Between 1957 and 2009, riparian vegetation grew into the river valley, and the river was allowed to meander widely.

The river channel is made up of alluvium and sand (the Qb and Qes). This loose sediment can be easily transported with high flows, resulting in rapid channel alteration. The area surrounding the river channel is primarily composed of shale groups. Shale is relatively prone to erosion, putting nearby infrastructure at risk of instability.

An example of such erosion-based risk can be seen where the river channel nears the Union Pacific Railroad (seen in the bottom left of image below). Erosion of the underlying shale could undercut the railroad foundation resulting in destabilization of the railroad structure. 

The land in the Sandoval region is covered primarily by grassland and herbaceous vegetation. This type of area is not typically subject to intensive agricultural management. On the east side of the bank, there is some shrub and scrub area–land with shrubs, young trees, or stunted trees that cover over 20% of the total vegetation. On the southwest side of the riverbank, there is an increase in urbanization as the river migrates southward towards the city of Pueblo, and land cover ranges from developed low intensity to developed high intensity. In high intensity areas, impervious surfaces account for up to 100% of the total cover. I-25 also runs alongside the west side of the river, which is designated as a developed low intensity area. Impervious surfaces found in cities and developed areas increase stormwater runoff, which can cause bank erosion and decrease groundwater recharge. In contrast, grassland and shrub area increases water infiltration into groundwater, which decreases bank erosion. The second figure represents impervious surfaces; on a scale of 0-1, black represents no impervious surfaces, and the color increases from light red to purple. Bright purple represents 100% impervious surface cover.

Our fluvial hazard zone includes area 2-8-2 19AC which is labeled on the plan to be a re-connected floodplain. We agree that this area is at risk of flooding and thus it makes sense to restore it as a floodplain.

Southwest of area 2-8-3 6AC, there is a building located within the fluvial hazard zone of Fountain Creek. If 2-8-3 6AC is re-established as a floodplain, this may increase the likelihood of flooding or channel migration west, toward this development. The owner of this property should be alerted of the risk of flooding in this area.

Area 2-8-1 24AC is currently at high risk of flooding. We agree that it makes sense to restore this area as a wetland, to reduce risk of flooding as well as bank erosion via sediment transport. Realignment of the channel in this area could also prevent bank erosion and recharge local groundwater. However, this would reconnect the active stream corridor to the floodplain proposed at 2-8-3 6AC. As previously mentioned, the landowner should be made aware of the risk of flooding that this will cause to the development in the area.

At the southernmost end of the Sandoval Focus Area, the active stream corridor (also the fluvial hazard zone) is very close to a railroad. Although the railroad is located at a higher elevation than the stream, this is a potential hazard to be aware of.