Stream power influence on southern Californian riparian vegetation

Abstract

Abstract. Mechanical damage by floodwaters is frequently invoked to explain the distribution of riparian plant species, but data have been lacking to relate vegetation to specific estimates of flood damage potential. This research uses detailed estimates of unit stream power (an appropriate measure of the potential for mechanical damage) in conjunction with vegetation cover data to test this relationship at 37 valley‐bottom sites in the Transverse Ranges of Southern California. A computer program, HEC‐2, was used to model the slope and the variation in flow depth and velocity of the 20‐yr flood across the sites. Regression models tested the influence of stream power (and of height above the water table) on the woody species composition of 393 4‐m cross‐section segments of the valley‐bottom sites. Results indicate that unit stream power does have a significant effect on the riparian vegetation, but that the amount of that influence and its importance relative to the influence of height above the water table varies between watersheds. Some species are found primarily in locations of high stream power, while others are limited to portions of the valley bottom that experience only low stream power.

Forecasting Environmental Responses to Restoration of Rivers Used as Log Floatways: An Interdisciplinary Challenge

“…Local-scale flooding and sediment deposition also contribute nutrients to riparian soils and facilitate the dispersion of riparian propagules (Nilsson and others 1991;Andersson and others 2000). In contrast, infrequent floods of high intensity or duration may denude large areas of riparian vegetation by dislodging or burying plants (Bendix 1999), or by creating anaerobic soil conditions (Blom and Voesenek 1996;Friedman and Auble 1999). Because floatway structures shield riparian plant communities from all but the most infrequent, catastrophic floods, their removal is expected to result in more frequent but less intense disturbance and correspondingly enhanced species richness.…”

A Field Guide to the Identification of the Ordinary High Water Mark (OHWM) in the Arid West Region of the Western United States: A Delineation Manual

“…(Lichvar and Wakeley 2004) to those that are influenced by the local landscape, which may vary laterally with distance from the center of the channel (lateral gradients in inundation duration and frequency, floodwater depth, etc.) (Stromberg 1993, 1998, Auble et al 1994, Stromberg et al 1996, Bendix 1999. Additionally, riparian plant community arrangements and distributions are controlled by local moisture availability and elevation, which are associated with increased precipitation, a higher abundance of vegetation, and the selection of certain assemblages and species (Lichvar and Wakeley 2004).…”

Restoration of Rivers Used for Timber Floating: Effects on Riparian Plant Diversity

“…Frequent low-intensity floods limit competitive exclusion by dominant species and create open patches for colonization by opportunistic species Grelsson 1990, Auble andScott 1998). In contrast, infrequent floods of high intensity or duration may denude large areas of riparian vegetation by dislodging or burying plants (Bendix 1999) or by creating anaerobic soil conditions (Blom andVoesenek 1996, Friedman andAuble 1999). Local-scale flooding and sediment deposition also affect soil composition and nutrient dynamics (Richards 1982, Naiman and De´-camps 1997) and facilitate the dispersion of riparian propagules (Nilsson et al 1991.…”