PREDICTING SOIL-SURFACE SEAL CONDUCTANCE FROM INCIPIENT PONDING AND INFILTRATION DATA

The objectives of this study were to determine: (1) the degree of seal development at incipient ponding, and (2) the relationship between the hydraulic conductance of developing seals and rainstorm characteristics, i.e. the rain intensity and kinetic energy rate. Laboratory columns of an Atwood soil (Typic Paleudalf) were subjected to rainstorms with different combinations of duration, intensity, and kinetic energy rate. Seal conductance was determined from measured infiltration data and a solution of the Richards' equation for vertical infiltration through an infinitely thin seal. The results show that the hydraulic conductance of the sealing zone decreased rapidly during early stages of rainfall commencing before incipient ponding. The analyses indicate that for storms of relatively brief duration (less than 2 h) the hydraulic conductance of the sealing zone depends on the cumulative rainfall energy and on the rainstorm intensity.