In 1996 the North Fork River Improvement Association was formed by landowners and river stakeholders concerned about decades of accelerated erosion along the North Fork of the Gunnison River. One of the first tasks of the newly-formed organization was to draft and publish a history and assessment of the river and the challenges faced by generations of farmers, ranchers and river users along the river. Jeff Crane, a local hydrologist and the first Director of the organization raised the money and performed the morphological assessment of the river.
The study focused on the various uses of the river and the effects different practices had on the integrity of the river system. Those practices included straightening the river with dynamite and bulldozers, excavating diversion structures for irrigation water and in-stream gravel mining. One of those in-stream gravel mines was located in Paonia just upstream of the State Highway 187 bridge. It began as a small family-owned operation in the 70’s and was eventually purchased by United Companies of Grand Junction in the late 80’s or early 90’s. Standard annual operating procedures included excavating river gravel from a large pit in the middle of the river during the late summer months while diverting the low river flows in a ditch around the north side of the river. The concept was to remove gravel in the late summer and fall and have the river replace what was excavated with natural sediment transport during the high spring seasonal runoff. However, local demand for gravel was much higher than the river could provide and that resulted in an annual down-cutting of the river bed.
A component of the morphological assessment included setting and surveying permanent cross sections along the river to measure rates of channel migration-both horizontally and vertically. At a different in-stream gravel mine near Hotchkiss, one of the cross sections measured six feet of channel down-cutting in one year between 1996 and 1997 approximately ¼ mile upstream of the site. United’s pit in Paonia also measured substantial down-cutting upstream of the pit but the more telling story was playing out just downstream of the pit at the highway b ridge. The assessment study obtained a photo of the bridge abutment from the USGS in 1992 that showed the bottom of the river channel at the top of the abutment’s pile cap-about where it should be. However, in 1997 a photo of the same abutment indicated over five feet of channel down-cutting in five years. The four foot thick pile cap was completely exposed and there was another foot to the river bottom. A thin person could have crawled under the bridge abutment. In essence, the bridge was now holding up the abutment instead of the other way around.
There are two processes at play that contribute to channel down-cutting both up and downstream of in-stream gravel mines. Channel headcutting vertically erodes the bed of the river channel upstream of the excavated pit. This happens as water pours over the entrance to the pit and erodes the bottom of the channel down to the level of the bottom of the pit as it migrates upstream until a balance is achieved between channel slope, velocity and sediment transport. The distance upstream that headcutting occurs is directly proportional to the depth of the pit. The deeper the pit the longer the headcut.
The other process is called the “hungry water” effect and it promotes channel down-cutting downstream of the pit. Every river has two primary functions. One is to drain the watershed and the other is to move sediment. When a river meets a large pit in the channel it loses its energy and sediment load into the pit. Once past the pit the river begins to scour the river bed to pick up more sediment to replace what it lost in the pit. That is what happened at the state highway bridge downstream of the gravel pit in Paonia.
When Jeff submitted this evidence to United Companies in 1997 they were legitimated concerned and shortly suspended in-stream operations at the site. The North Fork River Improvement Association worked closely with United Companies to develop a mining and reclamation plan at the site that was compatible with the river and its natural processes. An off-stream mine plan was developed until the site played out in 2001. In 2002 Jeff began negotiating with United to donate 19 acres of river and floodplain property to the North Fork River Improvement Association for use as the North Fork’s first public river park. In 2003 a memorandum of agreement was reached and in 2004 the company donated the property to the Association valued at $266,000.
A series of public planning processes began in 2005 to gage the community’s perception of appropriate uses for the property. A plan was created to develop the property downstream of Minnesota Creek as a high use area with picnic areas, a boat ramp, swimming hole and trails. The property upstream of Minnesota Creek was planned to be reconstructed as a natural area for wildlife and low-impact human day use.
For several years small projects in the high use area generated by volunteers and funded by small private grants dominated the extent of improvements at the park. The clean-up of the parking area, a bridge over Minnesota Creek, a primitive boat ramp, the removal of invasive plant species and a trail to the creek were implemented and public usage continually climbed. In 2008 Allan Comp, the director of the Western Hardrock Watershed Team held another series of public meetings and used the skills of VISTA volunteers to incorporate art projects into additional improvements in the high use area of the park. This resulted in a new steel entrance feature, an observatory deck, a bike rack and additional picnic tables. All the while plans were being developed to restore morphological integrity to the previous mining area that had developed into a series of braided channels.
Finally in early 2012 funding came through for the channel and floodplain restoration. The Bureau of Reclamation was funding a 5 mile ditch piping project for the Minnesota Ditch Company. The piping was anticipated to dry up many wetlands along the project site and was required by law to mitigate for the loss of those wetlands. The restoration of new wetlands and floodplain riparian areas at the river park was the perfect solution for the mitigation. By using the river park for mitigation the improvements stayed local. The Minnesota Ditch and Reservoir Company donated $166,000 and were matched by $62,000 from the Colorado Water Conservation Board, $35,000 from the Delta Conservation District and $12,000 from local in-kind donations to fund a comprehensive design and restoration of the previous mining area by Crane Associates.
In December 2012 the restoration construction was completed. The design reconnected a single thread meandering channel both up and downstream of the project area. The braided side channels were replanted with willows and filled to the bankfull elevation. The entire project site is designed to flood and deposit its sediment and seed base on the new floodplain. The primary channel was constructed with 4 grade control structures with a variety of fish holding and bank stabilization features. The width/depth ratio of the channel was reduced to lower average stream temperatures and provide pools during the extreme low water events of late summer. Five pieziometers have been installed to measure groundwater relative to stream flows and a rock amphitheater was constructed as an outdoor classroom for local students.