These are the beach profiles from group 1 to 8 (left to right except for 6 <right beside due to file size>). The nearer it gets to group 8's spot, the nearer it gets to mangrove area. As you can see, the further it gets away from mangrove forest, the more even surface it becomes. One of the reasons why this happens is that the mangroves are usually located at the beaches with very uneven surface, providing the local living creatures new environment so they can survive. However, the main reason why the surface gets uneven is because of longshore drift. It appears when the waves hit the beach and here the waves do not hit the shore straight on, it hits at an angle. As the backwash goes out, it takes some sand away with it. The current which goes the same way as the direction of waves, takes some of that suspended sand downshore. The current rarely changes because of prevailing winds, and therefore the sand typically never returns to its original location.