The spatial evolution of a directionally spread wave field on a near-planar natural beach is examined using data from longshore arrays of pressure sensors and wave staffs at 10.3 m and 4.1 m depth. High-resolution frequency-directional spectra from the deeper array are used to initialize a linear refraction model, and the resulting model predictions are compared with frequency-directional measurements at the shallow array. Linear theory inaccurately predicts both the shapes of directional spectra in shallow water and the total variances in some frequency bands. The discrepancies are largest for frequencies associated with maxima in the bicoherence spectrum, suggesting the importance of nonlinear effects. Furthermore, the measured directional spectrum at energetic low frequencies (0.05--0.11 Hz) and the vector resonance conditions for triads of long waves can be used to predict accurately the directions of observed peaks in directional spectra at higher frequencies (0.12--0.21 Hz). Prominent features in the measured directional spectra at the shallow array are thus consistent with energy transfers resulting from near-resonant triad interactions in the shoaling wave field. ¿ American Geophysical Union 1990