  The Square Kilometre Array (SKA) provides an excellent opportunity for low
cost searches for fast radio transients. The increased sensitivity and field of
view of the SKA compared with other radio telescopes will make it an ideal
instrument to search for impulsive emission from high energy density events. We
present a high-level search use case and propose event rate per unit cost as a
figure of merit to compare transient survey strategies for radio telescope
arrays; we use event rate per beam formed and searched as a first-order
approximation of this measure. Key results are that incoherent (phase
insensitive) combination of antenna signals achieves the highest event rate per
beam, and that 50-100 MHz processed bandwidth is sufficient for extragalactic
searches with SKA Phase 1; the gain in event rate from using the full available
bandwidth is small. Greater system flexibility will enable more effective
searches, but need not drive the top-level system requirements beyond those
already proposed for the SKA. The most appropriate search strategy depends on
the observed sky direction and the source population; for SKA Phase 1, low
frequency aperture arrays tend to be more effective for extragalactic searches
and dishes more effective for directions of increased scatter broadening, such
as near the Galactic plane.
