  In bosonic field theories the low-energy scattering of solitons that saturate
Bogomol'nyi-type bounds can be approximated as geodesic motion on the moduli
space of static solutions. In this paper we consider the analogous issue within
the context of supersymmetric field theories. We focus our study on a class of
$N=2$ non-linear sigma models in $d=2+1$ based on an arbitrary K\"ahler target
manifold and their associated soliton or ``lump" solutions. Using a collective
co-ordinate expansion, we construct an effective action which, upon
quantisation, describes the low-energy dynamics of the lumps. The effective
action is an $N=2$ supersymmetric quantum mechanics action with the target
manifold being the moduli space of static charge $N$ lump solutions of the
sigma model. The Hilbert space of states of the effective theory consists of
anti-holomorphic forms on the moduli space. The normalisable elements of the
dolbeault cohomology classes $H^{(0,p)}$ of the moduli space correspond to zero
energy bound states and we argue that such states correpond to bound states in
the full quantum field theory of the sigma model.
