If you’ve been on the beach anytime in the past couple of weeks, you’ve probably noticed that we’ve had day after day of wind running parallel down the beach. And then, occasionally, we’ve had extreme conditions over the weekend. This does some pretty interesting things to the bottom, which affect the safety of people that swim or wade in the water for quite a while.
The bottom within the surf zone has a memory. When current runs it picks up sand and moves it, causing a trench or trough, which is also known in “Galvestonese” as a “hole”. These are found consistently near structures like groins or piers and between the sand bars along the beachfront. These troughs can last hours to days, even after the conditions change significantly.
An example would be when wind blows parallel with the shoreline, causing a “littoral” or “longshore” current. This cuts deeper spots that run parallel to shore, forming our sandbar and trough system. This system is always there, but after a few days of strong current the difference between the sandbars and troughs is more pronounced. Deep troughs can be scoured out pretty close to shore. So, in extreme cases you can find water 5-6 feet deep only 15 yards from shore. Imagine the dangers for small children on these days. To make matters worse, when this is coupled with high surf, water from the waves can be pushed up to the shoreline and will have to find a way back out. If it breaks through a sandbar on the way out, more water follows, and it causes a trench perpendicular to shore that is a conduit for even more water to head back offshore. This causes a type of rip current called a “fixed rip”, which can last several hours.
Another example is that the groins and piers cause the water flowing parallel to head out away from the shore. This causes rip currents which are always there, called “permanent rips”. The deep spots near the rocks caused by all that water flowing out are responsible for water flowing out, maintaining the troughs, and causing danger, even on calm days. Water is lazy. It always seeks the path of least resistance.
A final danger imprinted in the “memory” of the bottom is “inshore holes” formed when larger/stronger waves break close enough to shore that they spill over, cut through the water, and smash into the bottom. These holes can be fairly deep. My daughter was body surfing with me a while ago, and we were laughing because I was up to my neck and she, while standing right next to me, was about waist deep.
As conditions calm, we’ll start seeing more normal bottom conditions after the sand jiggles back into place. For now, be extra careful.
The beach is a dynamic environment. This is why the guards are required to physically get in twice a day to check their area. That way they’re better able to spot trouble before it actually happens.