Using solid element roughness to control sand movement: Keeler Dunes, Keeler, California

- Roughness elements used to control sand flux to targeted reduction criterion.
- Observed sand flux reduction patterns corroborate empirical model prediction.
- Flux reduction due to decrease in magnitude of the flux not an increased threshold.
- Established relationships are robust predictors for estimating sand flux reduction.
- Roughness can be a cost-effective means to control sand flux and dust emissions.

The use of large roughness elements was investigated as a means to control sand transport and dust emissions in the Keeler Dunes to meet particulate matter air quality standards in Keeler, CA. 502 elements (straw bales) were arranged to mimic a natural vegetation pattern in a 50 × 100 m area in the dunes. The sand flux reduction target was 85%, compared to sand flux exterior to the array. Sand flux was initially reduced in the interior third of the array by ≈92% (±9%), exceeding the reduction target. Sand flux decreased exponentially with increasing distance into the array, reaching equilibrium at ≈110.5 element heights (≈42 m). Loss of effectiveness due to inundation of sand was 3.5% per month, falling below the target effectiveness after five months. The measurements of interior sand flux and rate of change of sand flux with increasing distance into the array corroborated the predictive ability of the empirical relationships used to design the roughness array. The established relationships are robust predictors for estimating how roughness modulates sand flux and can be used with high confidence for designing control strategies using this approach for roughness elements ≈0.3 m high for areas with low to modest topography.