A field-based parameterisation of wind flow recovery in the lee of dryland plants

Journal article

Wind erosion is a key component of land degradation in vulnerable dryland regions. Despite a wealth of studies investigating the impact of vegetation and windbreaks on windflow in controlled wind-tunnel and modelling environments, there is still a paucity of empirical field data for accurately parameterising the effect of vegetation in wind and sediment transport models. The aim of this study is to present a general parameterisation of wind flow recovery in the lee of typical dryland vegetation elements (grass clumps and shrubs), based on their height (h) and optical porosity (θ). Spatial variations in mean wind velocity around 8 isolated vegetation elements in Namibia (3 grass clumps and 5 shrubs) were recorded at 0.30 m height, using a combination of sonic and cup anemometry sampled at a temporal frequency of 10 s. Wind flow recovery in the lee of the elements was parameterised in an exponential form, (see article). The best-fit parameters derived from the field data were u0 = uref(0.0146θ - 0.4076) and u0 = uref(0.0146θ - 0.4076). By comparing this parameterisation to existing models, it is shown that wind recovery curves derived from two-dimensional wind fence experiments may not be suitable analogues for describing airflow around more complex, three-dimensional forms. Field-derived parameterisations such as the one presented here are a crucial step for connecting plant-scale windflow behaviour to dryland bedform development at landscape scales.

Authors: Mayaud, J; Wiggs, G; Bailey, R

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Earth Surface Processes and Landforms
• Volume: 42
• Pages: 378–386
• Publication date: 2016-11-08
• Acceptance date: 2016-11-03
• DOI: 10.1002/esp.4082
• EISSN: 1096-9837
• ISSN: 0197-9337
• Keywords: wind erosion; dryland vegetation; model parameterisation; flow recovery