Improve permeability and enliven the streets of the Mason University Corridor in Downtown Fort Collins through a strategy of improved storm water management and pedestrian connections.
Near what is now the town of Laporte, Camp Collins was established in 1862 by the 9th Kansas Calvary to protect the Cherokee trail and guard the Overland Stage Line. On June 9th, 1864 a devastating flood overtook the banks of the Cache la Poudre and wiped out the small military outpost; the search for a new location began. One of the first settlers of the area, Joseph Mason, suggested a place further downstream the river where the risk of flooding would be less. This new location would become what is present day Fort Collins. This narrative of the towns establishment is meaningful because for at least the next century the town and its economy would continue to be shaped by its relationship with the the Cache la Poudre.
Settlers, realizing the necessity of irrigation in this arid region, dug the first irrigation ditch to take water from the Cache la Poudre River in 1860. This important resource and the elaborate system of irrigation that would cover Larimer County from this point on would become the lifeblood of a rich agricultural region. The establishment of agriculture here would not be possible if it were not for the periodic flooding of the river and the fertile sediments that surrounding its banks.
threats to the Ecology of the Poudre river
The urban reach of the Poudre River is located in a unique geographical and ecological transition zone between mountain and plains ecologies and in its undisturbed state can support a unique and biodiverse blend of wildlife. The Poudre River system though has been highly modified by river management, utilization, and flood protection. The sum effect of river channelization, bank armoring and lower average peak flows has reduced the river’s capacity to scour banks, transport and deposit sediment, and interact with the floodplain. Native microorganisms, insects, fish, and vegetation have decreased in diversity since pre-settlement times, while non-native species have increased, with pollutant tolerant aquatic fauna predominating. Despite these changes, the roles of existing peak spring flushes and periodic flood years are believed critical to native biodiversity.
The Advisory Group anticipates a worsening of conditions to the river’s overall health within the Urban reach through Fort Collins primarily due to reduced spring flows and possibly reduced flows during low flow months. Over the course of time, the river is likely to look and behave more like a long, narrow lake bordered primarily by aggressive non-native trees and understory plants. Flood conveyance in this scenario may be compromised. Cottonwood forests along the river will become decadent more quickly due to lower groundwater levels and there will be an absence of younger forest age classes to replace them. These changes to the forest structure will reduce habitat for birds. Stagnant water reduces water quality which directly increases costs for water treatment in order for Fort Collins to meet Federal and State water quality standards. Finally, the reductions in peak flows may preclude future opportunities to restore habitat or ecosystem function of the river.
Changes in the Cache la Poudre morphology and flow regime have been brought about mainly by flood mitigation efforts. Urbanization greatly increases flood risk by drastically reducing pervious surfaces. Old Town Fort Collins was built very near and in some cases on top of the Floodplain. As a result Downtown Fort Collins has experienced severe flooding issues over the years.
The aim of the design for this project is to balance the goals of implementing a more robust storm water system through the corridor and that of improving the pedestrian experience through this area. Together these goals will combine to facilitate greater economic development and greater stewardship of the environment. A large portion of the corridor is inundated with high waters during heavy rainfall events, increased permeability through this area with the integration of bio filtration swales and permeable paving along the corridor and alleyways will add relief during storm events.
In keeping with our aim to improve the pedestrian experience we want the streetscape to take on a distinct character. This character is defined by a linear street profile which will allow sheet flow of water from impermeable surfaces into two bioswales on either side of the street. On-street parking along Mason street will be removed to make room for the inclusion of bio-swales and expanded sidewalks.
A strategy of bio-swales intercept excess storm water run-off during large storm events alleviating the current storm drain infrastructure. The proposed swales and permeable paving through the flood zone will allow greater infiltration to occur and plants and engineered soils will intercept heavy metals and biological toxins in contaminated storm water.