Utah Geological Association as part of their luncheon series titled 'The many hats of beaver: Ecosystem Engineer, Geologic Agent and Restoration Practitioner'.
North American beaver (Castor canadensis) were once trapped to near extinction for their pelts, which made fashionable top hats. Fortunately, for beaver and us, though extirpated in many areas top hats went out of fashion. Beaver populations are now recovering and we increasingly recognize their value as ecosystem engineers. Specifically, their dam building activities cause a cascade of hydrologic, geomorphic and ecological feedbacks that in-turn are critical to creating and sustaining complex, healthy habitat in rivers, streams and wetlands for a diverse range of flora and fauna. This recognition has elevated their status to a restoration practitioner in many parts of the country, including here in Utah, where beaver are actively used to help restore streams. From a geologic perspective, beaver excavate modest amounts of sediment to pack into their dams, but their dams and associated wetlands, floodplains and overfllow channels are sinks for massive quantities of sediment. In fact, in many of Utah's headwater streams (e.g. first to third order), the presence of valley bottoms is difficult to explain without the presence of beaver over the Holocene. That is, in what would otherwise be confined valleys, layers upon, layers of relic beaver dams filled in with sediment have raised up the valley floor. These beaver-pond and floodplain deposits do not have the same characteristics of traditional floodplains, and tend to exhibit a stepped morphology longitudinally, representing the forced nature of the flooding (i.e. forced by dams). We have taken advantage of these characteristics in incised channels and are using beaver to aggrade degraded systems and restore such channels. A mix of stories and anecdotes will be shared about the many hats of beaver, as well as some data and findings from some of our ongoing research into beaver and the profound geomorphic impact they have.