Intense bed-load, or sheet ﬂow, occurs when a free-surface ﬂow of water drives a thick, rapidly sheared layer of water and grains over an erodible granular bed. We examine here the transient case where ﬂow is induced by a sudden dam-break. Aiming for greater detail than achieved previously, we investigate this case using experiment and theory. The experiments combine particle tracking velocimetry (PTV) with a novel method of concentration measurement based on recording the penetration depth of a laser light sheet. The theory incorporates more vertical detail into the shallow water equations by using piecewise linear proﬁles of velocity and granular concentration, constrained by constitutive relations proposed recently for intense bed-load. These relations account for Coulomb yield at the bed, immersed granular collisions at the base, and equilibration of shear rate and density stratiﬁcation across the bed-load layer. Using these approaches, both experiment and theory yield time- and depth-resolved proﬁles of velocity and granular concentration in addition to longitudinal wave proﬁles. Without any parameter adjustment, the theoretical predictions are in good agreement with the experimental measurements.