Some effects of surface cover geometry on infiltration rate

Abstract

Infiltration into the soil is regulated in part by sealing of the soil surface by raindrop impact. Soil surfaces protected from such impact maintained higher rates of infiltration than exposed soil surfaces. It was hypothesized that the cover particles protected the covered portion of the soil and prevented the reaction of raindrop impact on the sot1 state. The soil under the cover particles remained in the original state in which infiltration could occur. However, since the cover particles in this study were impervious, infiltration could not occur on the covered area but would occur along the available perimeter of the cover particles. Water would then move in both vertical and lateral directions. The effective lateral distance that the water moved after entry was defined as the effective width. To evaluate the effects of soil surface cover on the infiltration rate of soils exposed to raindrop impact, simulated rainfall was applied at a constant rate to one soil type in small plots with free drainage, and square and rectangular cover particles of varying sizes and percentages were used as surface cover. THEORY AND PROCEDURE Infiltration involves three interacting phases:(1) the surface entry of water, (2) the available storage capacity of the soil, and (3) the movement of water through the soil profile. The surface entry of water controls the rate of infiltration during all periods when water can be stored in the soil or passed downward through the soil profile more rapidly than it can penetrate the soil. Generally the initial infiltration rate is high. The rate diminishes, however, during continued rainfall toward a nearly constant lower rate.The initial rate, the rate of decrease, and the final rate are affected by characteristics and conditions of the soil surface, soil profile, and rainfall.

Influence of rock fragment coverage on soil erosion and hydrological response: Laboratory flume experiments and modeling

“…This behavior—the short‐time increase of the mid‐ and larger‐sized particle sediment concentrations due to the rock fragments—was more pronounced for high rainfall intensity and low rock fragment cover (Figure 4, experiment H6) than for low rainfall intensity and high rock fragment cover (Figure 6, experiment H7‐E1). That is, while increasing water depth attenuates the raindrop impact, the force required to suspend the soil particles depends on grain size Koon et al [1970]…”

“…Additionally, they reduce the cross‐sectional flow area and rill development, resulting in increased flow path meandering and higher overland flow depths. During the early stage of a rainfall event, this increased overland flow depth leads to increased infiltration into protected areas around and under the rock fragments [ Adams , 1966; Koon et al , 1970; Poesen and Ingelmo‐Sanchez , 1992; Bunte and Poesen , 1994; Cerdà , 2001; Jomaa et al , 2012].…”

Effects of rock fragment cover on hydrological response and soil loss from Regosols in a semi-humid environment in South-West China

“…This leads to a decrease in the intensity of surface sealing, an increase in the infiltration rate, a decrease in the runoff volume, and, hence, a decrease in sediment production for soils covered by rock fragments. Parameters that have been reported to be important for explaining the degree of runoff or soil loss from soils containing rock fragments include the position (Poesen et al, 1990), size , geometry (Koon et al, 1970), and percentage cover (Mandal et al, 2005) of rock fragments and the structure of fine earth (Poesen and Ingelmo-Sanchez, 1992). De Figueiredo and Poesen (1998) suggest that the percentage of the rock fragment cover is the most important factor.…”

The contribution of rock fragments to the available water content of stony soils: Proposition of new pedotransfer functions

“…As far as the hydraulic functioning of soil is concerned, the rock fragments may influence the water storage (Cousin et al, 2003;Ugolini et al, 1998), the infiltration rate (Brakensiek and Rawls, 1994;Corey and Kemper, 1968;Grant and Struchtemeyer, 1959) and the surface evaporation regime (Groenevelt et al, 1989;Jury and Bellantuoni, 1976;Kemper et al, 1994;Koon et al, 1970;Poesen and Lavee, 1994).…”