Fan Lake Wetland Stabilization and Restoration Project
Contact: Kyle Patterson, 970-586-1363
Rocky Mountain National Park staff will begin work on a project that is designed to restore hydrologic, vegetative and habitat conditions at the confluence of Roaring River and Fall River. This area was dramatically altered during the Lawn Lake Flood.
On July 15, 1982, the man-made earthen dam at Lawn Lake failed. The subsequent flood sent raging water down the Roaring River, which scoured the river, inundated adjacent wetland habitat, and deposited a large debris fan at the confluence of the Roaring and Fall Rivers. Flood waters continued downstream in to Estes Park. Within Rocky Mountain National Park, a debris fan dammed Fall River at its confluence with the Roaring River, creating a 20 acre lake that flooded a willow carr, burying the willow beneath 10 feet of water and sediment. The lake, known as Fan Lake, became a popular fishing area.
In 1996, park officials determined that the debris fan was in danger of breaching, and there was growing concern that another flood could seriously impact Estes Park for a second time. At that time the National Park Service (NPS) prepared an environmental assessment, and the NPS Regional Director signed a Finding of No Significant Impact (FONSI) for the intentional breaching of a natural moraine so that Fan Lake could be drained under controlled conditions. The breach occurred in 1996 and the lake slowly began to recede.
Fan Lake now exists only as a small pond. The area that was historically occupied by a willow carr is now re-exposed, although significant changes have occurred as a result of the flooding. Most notably, large areas of riparian willow have been lost and the former Fan Lake area consists of bare sediment, open water, or marsh wetlands. Willow have not reestablished themselves in these areas in the 10 years since Fan Lake started to recede.
During site visits by park staff and wetland restoration experts in 2005 and 2006, it was determined that the formation and persistence of Fan Lake had significantly altered topographic, soil and hydrologic conditions, making restoration to historic conditions impossible without restoring the site’s hydrologic regime. Even with reestablishment of the hydrologic regime, willow could not be restored without excluding elk. Therefore, this project proposes to restore the Roaring River to its former channel, conduct further work on Fall River, replant native willow and sedge species, and build an elk exclosure to protect the new plantings.