How did the Qattara Depression help British forces defend El-Alamein?

The Qattara Depression served as a vital natural barrier that helped British forces defend El-Alamein by acting as an impassable anchor at the southern end of their defensive line.12

Because the depression consists of salt lakes, marshes, and terrain that is impassable to military traffic, it effectively closed off the southern flank of the 40-mile-wide corridor between the Mediterranean coast and the desert. This geography created a bottleneck that prevented Erwin Rommel’s forces from outflanking the British position, forcing them to attack the prepared defensive line head-on. By securing this flank, the British were able to concentrate their defenses and successfully halt the German advance into Egypt in July 1942.123