Large wood addition for aquatic habitat rehabilitation in an incised, sand‐bed stream, Little Topashaw Creek, Mississippi

Abstract

Large wood (LW) is a key component of stream habitats, and degraded streams often contain little wood relative to less-impacted ones. Habitat rehabilitation and erosion control techniques that emphasize addition of natural wood in the form of individual elements or structures are increasingly popular. However, the efficacy of wood addition, especially in physically unstable, warmwater systems is not well established. The effects of habitat rehabilitation of Little Topashaw Creek, a sinuous, sand-bed stream draining 37 km 2 in northwest Mississippi are described herein. The rehabilitation project consisted of placing 72 LW structures along eroding concave banks of a 2-km reach and planting 4000 willow cuttings in sandbars opposite or adjacent to the LW structures. Response was measured by monitoring flow, channel geometry, physical aquatic habitat and fish populations in treated and untreated reaches for 2 years before and 4 years after rehabilitation. Initially, LW structures reduced high flow velocities at concave bank toes. Progressive failure of the LW structures and renewed erosion began during the second year after rehabilitation, with only 64% of the structures and about 10% of the willow plantings surviving for 3 years. Accordingly, longterm changes in physical habitat attributable to rehabilitation were limited to an increase in LW density. Fish biomass increased in the treated reach, and species richness approximately doubled in all reaches after rehabilitation, suggesting the occurrence of some sort of stressful event prior to our study. Fish community composition shifted toward one typical of a lightly degraded reference site, but similar shifts occurred in the untreated reaches downstream, which had relatively high levels of naturally occurring LW. Large wood is a key component of sand-bed stream ecosystems, but LW addition for rehabilitation should be limited to sites with more stable beds and conditions that foster rapid woody plant colonization of sediment deposits.

Wood placement in river restoration: fact, fiction, and future direction

“…Studies in low-gradient (<1.5%) streams such as those in the US Midwest or western Europe have demonstrated physical habitat changes, including increased depth, cover, narrower channels, and increased organic matter retention, as a result of wood placement projects (e.g., Gerhard and Reich 2000;Hunt 1988;Laitung et al 2002;Zika and Peter 2002). Other projects designed to aggrade incised stream channels have produced increases in water depth, width, pool area, and bed elevation (reduced incision) (Newbury and Gaboury 1988;Shields et al 2004Shields et al , 2006.…”

Structure and function of large wood in Ozark headwater streams and its relationship to fish community structure

“…In the US stream restorations that include the addition of LW have been conducted in various regions including the Midwest (Moerke and Lamberti 2003;RosiMarshall et al 2006;Entrekin et al 2008;Hrodey and Sutton 2008), Pacific northwest (Levell and Chang 2008), western (Kauffman et al 1997), and southeastern (Wallace et al 1995;Shields et al 2006) states. In fact, most managers cite creation of fish habitat as the number one objective of stream restoration (Kail et al 2007); however, fish responses have varied among studies.…”

A dimensionless statistical analysis of logjam form and process

“…The hydrological and geomorphological function of individual logjams shows a great deal of variability, can change with river stage, and shows only weak correlations with physical parameters of the structure (Dixon, 2013). Although the importance of logjams for stream diversity and ecological health has been recognised and the insertion of engineered logjams is a widespread river restoration technique (Brooks et al, 2004;Bernhardt et al, 2005;Shields Jr et al, 2006;Collins et al, 2012), the features of individual logjams which are correlated with the creation of additional geomorphological or hydrological diversity remains unknown (Klaar et al, 2009;Dixon, 2013) and restoration techniques typically rely on increasing general geomorphic complexity .…”