Alluvial fan sage scrub is a shrubland type made up predominately of drought-deciduous soft-leaved shrubs that occur on alluvial soils undergoing repeated sediment deposition from relatively frequent periodic flooding. Alluvial scrub is most typically found in alluvial washes, on gently sloping alluvial fans, and in the active floodplains of the valley floor. Several Covered Species have a high affinity for alluvial soils and the associated shrubland in the Planning Area, including San Bernardino kangaroo rat, Los Angeles pocket mouse, slender-horned spineflower, and Santa Ana River woolly-star.