Effectiveness of an array of porous fences to reduce sand flux: Oceano Dunes, Oceano CA

Arrays of porous fences, ≈12 ha in 2014 and ≈ 15 ha in 2015, were constructed in the Oceano Dunes State Vehicular Recreation Area to evaluate their effectiveness to reduce sand flux and affect local PM10 dust concentrations. The 1.22 m high, ≥244 m long, ≈50% porous fences were placed 10 fence heights apart in 2014 and 7 in 2015. Measurements of sand flux through the arrays indicated that it diminished exponentially with increasing distance, reaching equilibrium at ≈93 fence heights for the 10 h spacing and ≈27 fence heights for the 7 h spacing. Fences spaced 7 h apart reduced sand flux for the entire area by 78%, and 86% for the area ≥27 h. Fences spaced at 10 h reduced sand flux for the entire area by 40%, and 56% for the area ≥93 h. PM10 monitoring upwind and downwind of the array and in the absence of the array in 2015, indicated that the downwind PM10 concentration was less than the upwind for the fence array, whereas in the absence of fences PM10 increased in the downwind direction over the same fetch distance, suggesting the presence of the fences was reducing the flux of PM10 from within the fence array.