Stream Ecosystem Recovery Following a Catastrophic Debris Flow

Abstract

We studied recovery processes for 3 yr in Quartz Creek (Cascade Mountains, Oregon), a third-order stream catastrophically impacted by a February 1986 debris flow for which both predisturbance data and an upstream control reach were available. The debris flow altered channel geomorphology and destroyed riparian vegetation for 500 m, resulting in a reach with short, disordered channel units, low hydraulic retention, and an open canopy. High irradiance levels and reduced grazing by macroinvertebrates contributed to rapid accrual of benthic algae in the disturbed reach, which formed the bioenergetic basis for ecosystem recovery. Macroinvertebrates (mostly herbivores) recovered to upstream densities and taxonomic richness within 1 yr, although effects on community structure persisted into the second year. Cutthroat trout (Oncorhynchus clarki) populations were locally decimated by the disturbance, but by the following year, recruitment of young-of-the-year trout into the reach exceeded that of the upstream reach and populations had recovered to predisturbance densities. Despite the general rapid recovery of the biota within the disturbed reaches, most populations showed broad temporal fluctuations in abundance, suggesting that ecosystem stability was diminished by the debris flow. Long-term monitoring of Quartz Creek may yield additional insight into the role of episodic disturbance in stream ecosystems.

The succession dynamics of a macroalgal community after a flood disturbance in a tropical stream from São Paulo State, southeastern Brazil

“…Lamberti et al (1991) observed, during recolonization process in a flood perturbed stream, an immediate decrease in global abundance of the benthic algal community followed by rapid increase. According to the authors, the disturbance promoted extensive environmental changes that resulted in higher light availability and an increase in local primary production.…”

“…However, the organisms that inhabit in running waters need mechanisms to avoid or resist mechanical stress caused by water flow (Gordon et al 1992). Thus, several authors have suggested that the disturbance produced by current velocity is very important to the settlement and maintenance of the periphytic biomass in lotic ecosystems (Horner & Welch 1981, Steinman & McIntire 1986, Lamberti et al 1991, Uehlinger et al 1996.…”

Winter Disturbances and Riverine Fish in Temperate and Cold Regions

“…Flashiness is further influenced by the water storage capacity of the snow, which is a function of temperature (Swanson et al 1998): Warm and wet snow layers melt more quickly, whereas cold and dry snow stores rainwater in the early phase of a rain-on-snow event, attenuating the rise in discharge. In systems with steep hillslopes, winter rainstorms can trigger debris flows, which can deliver masses of soil, sediment, and wood to nearby streams (Lamberti et al 1991). Furthermore, across an altitudinal gradient, dynamic ice formation such as excessive anchor ice growth is found only in midelevation reaches (e.g., 2550-2900 meters [m] above sea level [asl] in Wyoming streams, 41 degrees, 2 minutes north latitude) with an incomplete snow and surface ice layer (Chisholm et al 1987).…”

“…Debris flows, which can be triggered by extreme winter rainstorms, can result in fundamental alterations of riverine habitats through the modification of pool-riffle sequences through scour, which can lower the stream gradient through the deposition of sediment and wood behind a debris dam and can increase irradiance through the removal of riparian vegetation (Swanson et al 1998, Lamberti et al 1991. Snow avalanches can represent a pulse disturbance (Resh et al 1988), locally depositing large amounts of snow and trees, which could temporarily evoke similar effects on aquatic habitats as debris flows.…”

Movement and Mortality of Adult Brown Trout in the Motupiko River, New Zealand: Effects of Water Temperature, Flow, and Flooding

“…We actually observed a similar reduction (65%) in juvenile brown trout abundance, resulting from the same March 2005 flood in the Rainy River, a tributary of the Motupiko River (J. Hay and J. W. Hayes, unpublished data). Channel morphology appears to influence the effects of floods on salmonids, greatest changes in abundance occurring at sites where bed load movement and geomorphic changes occur (Lamberti et al 1991;Pearsons et al 1992;Nislow et al 2002). Substantial bed load movement and removal of riverbed and bank vegetation were evident in the Motupiko and Rainy rivers as a result of the flood.…”