A high capacity flood pump system includes a floodwater diversion pathway; a pump assembly above the floodwater diversion pathway, the pump assembly including a flood pump having a pump housing with a pump housing inlet and a pump housing outlet; an impeller housing disposed in fluid communication with the pump housing between the pump housing inlet and the pump housing outlet, the impeller housing disposed beneath the pump housing; at least one impeller disposed in the impeller housing; and a power unit drivingly engaging the at least one impeller.