Why couldn't Israel have crossed the Red Sea at the shallow reedy top end?
The shallow, reedy top end was not wilderness but populated land, so it did not match the route God led Israel through. The wilderness only approached farther down the Red Sea. Crossing there would also require only 18 inches of water, which would hardly constitute the miraculous deliverance described.
Les explains that the top end of the Red Sea, where the water is only about 18 inches deep and reeds grow, is not wilderness but populated territory. The wilderness does not begin until farther down along the Red Sea. Since God led the people through the way of the wilderness of the Red Sea, the crossing had to occur at the deeper portion. Les is convinced they crossed there because going through 18 inches of water would not be much of a miracle. The surrounding geography also matters: the Red Sea was in front, forbidding mountains to the right, population to the left, and Pharaoh's army coming from behind. Thus the shallow reedy top end was unsuitable both geographically and miraculously.