Assessing the Role of Ash in Rainfall Runoff Dynamics in Fire Affected Soils in Vall D'albaida. Part 2. Laboratory Rainfall Simulation Experiments.

Measurements by means of natural and simulated rainfall in the field can measure surface runoff but infiltration is calculated. Direct measurements of infiltration, subsurface flow and percolation are rare. Laboratory experiments allow measurements of overland flow or subsurface flow, infiltration and percolation. Plots of 20 cm x 50 cm x 100 cm were used to measure surface runoff, subsurface runoff and percolation. The boxes were filled with gravel (2 cm in diameter) for the first 10 cm, and the upper 10 cm was filled with soil collected in the study area of Vall d’Albaida (Municipality of Ontinyent), and finally a cover of ash with 0, 20, 40, 60, 80 and 100 % at different depth 0, 1, 2, 3 and 5 cm (from the Ontinyent 2010 forest fire) was applied on 90 experiments (3 plots x 6 covers x 5 depths). Rainfall simulated experiments were carried out at 55 mm h-1 on dry soils during one hour. Runoff, infiltration and percolation was collected every minute. Every 5 minutes, runoff samples were desiccated and sediment loads were measured. From the runoff discharge and the sediment concentration the soil erosion rates were calculated. The results show that the ash cover and ash depth control the rainfall- runoff dynamics and with that also the erosion potential. The experiments showed that subsurface flow was negligible, and percolation non-existent. GL2008-02879/BTE, LEDDRA 243857 and RECARE (nº 603498, http://recare-project.eu/), iSQAPER (H2020-SFS-2014-635750-2) and CGL2013-47862-C2 supported this research.