This paper presents a stochastic model of the joint depth and velocity probability distribution in stream channels. Model input is restricted to simple measures of channel geometry. Hydraulic distributions are quantified using two independent hydraulic variables, each a function of velocity and depth, and varying either longitudinally or laterally within a stream channel. The stochastic model provides a useful tool for exploring relations between fine-scale hydraulic variations and channel geometry. One application is modeling fine-scale hydraulic habitat conditions in stream channels.