Interactions between waves, bank erosion and emergent vegetation: an experimental study in a wave tank

Abstract

Emergent vegetation development, wave extinction and soil erosion are strongly interrelated processes in exposed riparian zones. The above-ground parts of the vegetation reduce wave energy, while the below-ground parts strengthen the soil. On the other hand, vegetation development may be restricted as a result of wave stress. Interactions between waves, soil erosion, and emergent vegetation were studied during three consecutive years. Two helophyte species, Phrugmites australis (Cav.) Trin. ex Steudel and S&pus lucustris L., were planted in separate bank sections on two types of sediment, sand and silty sand, in a wave tank. Regular waves were transmitted through 4 m wide bank sections with and without helophytes growing on a horizontal part. Bank profiles, wave transmission patterns and vegetation parameters were measured after exposure to waves with a height of 10 cm (Year 1) and 23 cm (Years 2 and 3). Both 10 cm and 23 cm waves affected bank profiles. Erosion of the banks occurred due to downslope transport of sediment. Soil erosion patterns closely reflected the patterns of standing waves over the horizontal part of the bank. Emergent vegetation influenced the erosive impact of waves by both sediment reinforcement and wave attenuation. A smaller amount of net erosion was measured in the wave-exposed sections covered by vegetation than in the unplanted sections. The stands of Scirpus lucustris were damaged due to uprooting of rhizome parts by 23 cm waves, followed by increased erosion of the soil. No damage occurred to the Phragntites australis stands. The greatest ' Cortespondiig author.

Ecology of freshwater shore zones

“…13 Idealized relationships between beach geomorphology, ecological processes, and aquatic macroinvertebrates along sandy beaches (modified from Defeo and McLachlan 2005). Beach types are arranged from highly reflective to highly dissipative Fig. 14 Effects of Phragmites australis on wave attenuation and bank erosion in an experimental wave tank (Coops et al 1996). Waves approach from the right mineralization of wrack can be an important source of nutrients to nearshore microbes and phytoplankton (Malm et al 2004), as well as terrestrial microbes and vegetation.…”

Wave Damping in Reed: Field Measurements and Mathematical Modeling

“…The wave damping effects by common reed (Phragmites australis) has been investigated together with another emergent species (Scripus lacustris) in a tank experiment by Coops et al (1996) to analyze the potential for erosion protection from ship-induced waves at river banks. They showed that Phragmites australis reduced the wave height most effectively and this reed was also most capable to withstand the wave energy, while Scripus lacustris was damaged.…”

Physical modelling of water, fauna and flora: knowledge gaps, avenues for future research and infrastructural needs

“…In the Mediterranean, leaf litter commonly gets washed up on beaches, with up to 2 m of vertical accumulation, significantly reducing wave impact and erosion caused by waves and currents (Simeone and De Falco 2012). However, it remains unclear whether (i) flow and turbulence fields are always modified in a way that reduces erosion and/or enhances deposition and (ii) there are particular species, assemblages of species, stem, leaf and stand configurations and/or areal extents needed to sustain or attenuate hydrodynamic forcing (Coops et al 1996). In addition, further study is needed to document and quantify the complex response of the coastal ecosystem when leaf litter is removed.…”