  In analogy with ocean waves running up towards the beach, shoaling of
prechirped optical pulses may occur in the normal group-velocity dispersion
regime of optical fibers. We present exact Riemann wave solutions of the
optical shallow water equations and show that they agree remarkably well with
the numerical solutions of the nonlinear Schr\"odinger equation, at least up to
the point where a vertical pulse front develops. We also reveal that extreme
wave events or optical tsunamis may be generated in dispersion tapered fibers
in the presence of higher-order dispersion.
