We propose a survivable SDM optical network architecture that adopts dedicated path protection and spatially-jointed flexible waveband routing. With a proposed heuristics-based design algorithm that considers the limited number of flexible wavebands, we can achieve almost identical routing performance to conventional optical networks while reducing the hardware cost. Numerical simulations on several topologies elucidate that the number of flexible wavebands, equals to the degree of WSSs in the spatially-jointed switching mode, can be small. The total number of necessary WSSs is successfully reduced by 75%/91% relative to conventional SDM networks with core-wise/spatially-jointed switching nodes.