Wind erosion of blanket peat during a short period of surface desiccation (North Pennines, Northern England)

Abstract

Strong winds are a characteristic feature of UK upland areas. Despite this, understanding of aeolian processes in upland environments of the UK is limited. This paper presents direct measurements and observations of blanket peat erosion by wind action during a two week period of desiccation in the North Pennines, Northern England. A circular configuration of mass flux sediment samplers was used to collect peat eroded by wind action from 16 cardinal compass directions. Meteorological conditions (wind speed, wind direction, precipitation and temperature) were recorded by an automatic weather station set up adjacent to the site. Surface desiccation led to peat crust erosion and dust deflation. During short (≤ ≤ ≤ ≤ ≤1 hour) periods of precipitation, wind-driven rainfall also caused erosion. Typically, dust flux rates were up to two orders of magnitude lower than recorded during periods of sustained wet weather. Measurements demonstrate the hitherto unreported rapid switch in process regime between wind-driven rainfall and dry blow deflation in blanket peat environments. Dry blow processes of blanket peat erosion may become more important in UK upland areas if climate change promotes more frequent surface desiccation. Figure 3. Precipitation and temperature data recorded at Moss Flats using the automatic weather station (AWS). Desiccation processes were measured and observed between 13 and 27 May 2004 (indicated by the shaded box).desiccation conditions developed. Second, although rainfall totals and intensities were low during the dry period, average (0·14 m s −1 ) and maximum (0·34 m s −1 ) wind friction velocities were very similar to those recorded during periods of sustained wet weather. The friction velocity series (Figure 4) shows both diurnal peaks and discrete wind storms when the potential for wind erosion was at a maximum. Wind erosion of blanket peat during surface desiccation 485Erosion of the desiccated peat surface through crust detachment was directly observed at Moss Flats. Crust edges acted as the foci for wind action (Figure 1), which proceeded to detach platy peds through mechanical crust rupture. Crusts attached at the surface varied in width from ca. 40 to 250 mm. Once detached, entrained peds were observed moving by saltation and were found deposited in vegetation (Eriophorum) surrounding the eroding surface. Deposited crusts were typically smaller (ca. 20 -100 mm) than those attached at the surface, and varied in dry weight between 2 × 10 −4 and 4·4 × 10 −3 kg −1 , with a mean of 1·75 × 10 −3 kg. As well as direct observation of crust erosion, fine peat dust was observed blowing up to 1·87 m above the surface.

Average sand particle trajectory examined by the Raindrop Detachment and Wind‐driven Transport (RD‐WDT) process

“…Vieira et al (2004) presented the influence of oblique rainfall on the genesis of coarse sand accumulations and emphasized the importance of RD-WDT as a main transportation mechanism. The importance of the process on blanket peat erosion was signified by Warburton (2003), Evans and Warburton (2005) and Foulds and Warburton (2007a). Foulds and Warburton (2007b) found that dust flux rates by saltation were in general up to two-orders of magnitude lower than that recorded during periods of sustained wet weather.…”

Microtopography of bare peat: a conceptual model and objective classification from high‐resolution topographic survey data

“…Erosion by flowing water is the dominant component in most UK peatlands; but local topography exerts a strong control in determining process dominance (Evans and Warburton, 2007). Bare peat surface microtopography is especially dynamic and patchy; different surface processes leave distinctive topographic roughness signatures and local surface microtopography can adjust rapidly in response to changing processes over relatively short timescales (Foulds and Warburton, 2007). Bare peat surface microtopography is especially dynamic and patchy; different surface processes leave distinctive topographic roughness signatures and local surface microtopography can adjust rapidly in response to changing processes over relatively short timescales (Foulds and Warburton, 2007).…”

Potential Use of BEST® Sediment Trap in Splash - Saltation Transport Process by Simultaneous Wind and Rain Tests

“…Although there are accumulated works performed under controlled laboratory conditions for essentials of WDR erosion processes, field studies and observations are still very rare [7–9] particularly for the splash-saltation transport process. The reason is that, despite the fact that a certain number of active and passive aeolian sediment traps for wind-driven sediment transport exist, there has been no trap specifically designed to catch and quantify splash-saltating particles during rainfall events accompanied by strong winds previously.…”