This document proposes a new unsupervised algorithm-level fusion scheme (UAFS-HCD) to improve the accuracy of pixel-based change detection in multitemporal SAR flood images. The scheme first uses pixel-based change detection to get a preliminary change mask and estimate parameters for object-based change detection. It then derives an unchanged area mask to eliminate areas without changes, reducing errors. Finally, it obtains a final change mask using object-based change detection. When tested on flood detection, the new scheme was more accurate than traditional pixel-based, object-based, and other hybrid change detection methods.