  In this paper we prove a nonautonomous chain rule formula for the
distributional divergence of the composite function
$\boldsymbol{v}(x)=\boldsymbol{B}(x,u(x))$, where $\boldsymbol{B}(\cdot,t)$ is
a divergence--measure vector field and $u$ is a function of bounded variation.
As an application, we prove a uniqueness result for scalar conservation laws
with discontinuous flux.
