Assessment of vegetation effects on hydraulics and of feedbacks on plant survival and zonation in ephemeral channels

Abstract

Abstract:The interaction of vegetation and flow in channels is important for understanding the influences of forces in channels and effects on erosion, sediment flux and deposition; it has implications for channel habitats, channel instability and restoration schemes. Methods are needed for calculating forces on plants and data are required on thresholds for plant destruction and survival. A simple method of calculating the effect of hydraulics on vegetation and its zonation within ephemeral channels is described. Detailed cross section surveys of channel morphology, vegetation and estimates of Manning's n are input into the software program WinXSPRO to calculate the hydraulics of flows across the channel for a given event or flow level, incorporating subdivision into zones of differing morphology and vegetation across the section. This was applied to a number of cross sections on ephemeral channels in SE Spain and typical roughness values for Mediterranean vegetation types in channels were assessed. The method is demonstrated with reference to two well-documented floods in SE Spain, in September 1997 on the Torrealvilla and in October 2003 along the Salada. These flows led to the mortality of herbs, reed and smaller shrub species. Some damage to larger shrubs and trees occurred, but trees such as Tamarisk (Tamarix canariensis) were shown to withstand high forces. Some grasses were highly resistant to removal and induced sedimentation. Significant erosion was limited to areas with little vegetation covering the channel floor. Further quantification of resistance of vegetation to flows and upper threshold values for removal is continuing by relating calculated hydraulic conditions using the methods outlined to measurements of vegetation responses in events at monitoring sites.

Evidence of increase in woody vegetation in a river corridor, Northwest England, 1984–2007

“…River corridors are prime locations for maintenance of such connected habitats, and riverbanks can be refuges (Smart et al, 2005). The presence of riparian vegetation delivers many benefits, and much recent research has also been stimulated by a need for greater understanding of dynamics in order to implement protection and restoration (Bennett, Wu, Alonso, & Wang, 2008;Richter & Richter, 2000;Sandercock & Hooke, 2010;Schirmer et al, 2014;Tabacchi, Steiger, Corenblit, Monaghan, & Planty-Tabacchi, 2009). …”

“…Stromberg, Lite, & Dixon, 2010). Types and zonation of riparian vegetation are strongly controlled by hydrological regime (Osterkamp, Hupp, & Stoffel, 2012;Sandercock & Hooke, 2010;Tabacchi et al, 2009), and occurrence of floods can affect recruitment and survival (Pasquale, Perona, Francis, & Burlando, 2014;Perona et al, 2009). Succession, particularly on river bars, is well known .…”

Point Cloud Data Fusion for Enhancing 2D Urban Flood Modelling

“…The conventional levelling telescopes, total stations (Ballesteros Cánovas et al, 2011), GPS equipment (Sandercock & Hooke, 2010) or laser range finders (Denlinger et al, 2002) can be adequately used for this purpose. However, identification the peak of flood watermarks is often subject to considerable error (Marchi et al, 2009) and requires skill to identify the highest water level accurately.…”

European Tamaricaceae in Bioengineering on Dry Soils

“…Saltcedars with their deep roots are known to be extremely resistant to shear stress (beyond 400 Nm -2 ) and erosion by streams, while most of the other species associated with saltcedars in Mediterranean environments (herbaceous, helophytes, and the other small shrubs) get uprooted (Sandercock and Hooke 2010). Nevertheless, Mg produced a lower root quantity and less biomass Numbers of individuals for belowground biomass (no stress, stress): Mg (11,11),Sp (9,12),Tg (8,12) Environmental Management (characteristic of this thin-stalked species) than Tg and Sp.…”

“…Although their use in bioengineering has been poorly assessed, in Europe, there are initiatives aiming to preserve or reintroduce them. Myricaria germanica and different species of genus Tamarix have been shown to be resistant to sedimentary denudation or burial (Müller and Scharm 2001;Qong et al 2002;Sandercock and Hooke 2010) and floods (Tallent-Halsell and Walker 2002;Kumari 2008;Kudrnovsky 2013). The fact that they can establish themselves in perturbed environments as well as the results of some bioengineering experiments indicate good resprouting capacity (Schiechtl 1980;Venti et al 2003;Koch and Kollmann 2012).…”