River Information: A short history of dams on the San Marcos River by Tom Goynes


All of the dams on the San Marcos River are approximately the same age (about one hundred years) they were all built in a similar manner, and they all seem to be falling apart at the same time.

The construction technique was to dig a ditch down to and into the blue clay. Next, post holes were dug into the blue clay and cedar fence posts were erected. Then some sort of wooden structure was constructed. At this point, a few of the dams were poured with concrete (Cummings Dam and Martindale dam are such examples) Some of the dams were simply made of rocks and wood.

After a century, the cedar seems to be failing. And in some instances, the structures are eroding underneath, allowing water to pass beneath the wood and/or concrete and through the blue clay.

Here is a brief history of some of the dams along the San Marcos

First of all, Spring Lake Dam is just upstream of City Park. That's where SWT causes us grief by raising the level of Spring Lake (for reasons only they could explain) and reducing the flow of the springs. It has been decomposing for some time, but SWT claimed it was damaged by the flood of October 1998. Senator Kay Bailey Hutchison helped SWT secure federal money (FEMA) to repair the dam (she claims it is a flood control dam - go figure). We taxpayers will spend $200,000 for emergency repairs and probably ten million for permanent repairs unless someone, somewhere comes to his or her senses. Spring Lake Dam is in a continual state of "imminent danger of collapse" by order of the TNRCC. Therefore anyone who ventures too close will be arrested by school police.

The first dam below City Park is Rio Vista Dam. It is the only dam on the San Marcos River that I consider runnable. It has a neat little slot just to the right of center and a ledge which turns the water downstream rather than allowing it to form a reversal or hydraulic. We have used it as an example for people who are interested in building a "safe" dam. While it has a good bit of surface decay, overall it seems to be holding up pretty well. Every now and then someone claims that it is about to fall apart, but then it lasts another decade, so the imminent danger thing has never been much of an issue here.

The next dam is the one that has been causing the latest interest. It is just below IH 35, at the start of Thompson's Island. I call it Cape's Dam, because Mr. Cape was the previous owner, and the private camp on the left side of the river at that point is called Cape's Camp (it's a place that can be reserved for parties and other shindigs). It is currently owned by the Thornton family in San Marcos - I believe Russell Thornton is the latest contact.

There is a man made mill race going left at the beginning of Thompson's Island. Supposedly it was dug by slaves about the time of the Civil War. The mill race actually forms the island. At the bottom of the mill race is another dam which we generally call Thompson's Island dam. It blew out three years ago and was repaired by your state government, in fact by the TP&WD, to the tune of approximately $300,000. A couple of years before it blew, the owner of that dam (John Stokes) donated the dam and the lower portion of Thompson's Island to the TP&WD for use as a park. Supposedly (according the Stokes family at least) there was a gentlemen's agreement between the Stokes family and TP&W that if the dam ever collapsed, TP&W would repair it. You see, the Stokes family still owns the high ground at the dam and plans to put in some condos some day. At any rate, once the dam blew the Stokes family demanded that the dam be repaired and eventually it was. I suppose one of the reasons that TP&W wants to register canoes is to pay for such things as dam repairs. Perhaps they should register dams instead. Another interesting tidbit regarding the Thompson's dam blowout is that when it happened, Mr. John Thornton (Russell's dad) was totally uncooperative with TP&W and the City of San Marcos and wouldn't even let folks access his dam to put up warning signs. I had to take the fire chief in from above by canoe. But I digress....

Let's go back to Cape's (or Thornton's) dam. It is a wood and rock structure with a few pieces of railroad rail driven in here and there for good measure. Years ago, back in the early 70's we canoeists used to rearrange the rocks in that dam on a regular basis to make it more runnable. After all, it appeared to us at the time to be an abandoned structure, and no one ever told us otherwise. There was very little lake upstream of the dam. Knowing what we know now about wild rice - that it has to have the dams on the San Marcos to survive - I'm amazed it made it. Perhaps wild rice has evolved and now, after billions of years of preferring a river with current, it now prefers stagnant ponds. At any rate, our puny efforts at dam removal were short lived. The Thornton's eventually rebuilt the dam with fresh rocks and stretched Hurricane fence over the top of it so that we couldn't move the rocks again. In fact, they raised the level of the dam so much that we had to start portaging the old black sewer pipes that used to cross the river at IH 35. I complained to the Thornton's and to the State, but to no avail. Capes Dam was back, bigger than ever.

But years have a way of destroying dams. Now the Hurricane Fence has decomposed and the cedar is rotting. Last winter the dam had a major blowout and the USF&WS spent some more of our tax dollars on Cape's Dam. Of course, before they "repaired" the dam with cement bags, they ripped up all the endangered wild rice by hand (killing most of it I'm sure) and transplanted it in the federal fish hatchery for "safe keeping". The plan is to re-introduce it once they return the river to its natural condition - that is dammed.

There is no question it will make a great rapid. I have already been in contact with the USF&WS to request that the dam be removed. While the current administrator (a fellow named Bill Sewell) seems to have a love for dams, I still have hopes that somehow a more reasoned person may prevail. But I have asked for a voice if and when that dam is ever "permanently" repaired. I have already gone on record saying that if any more tax dollars are to be spent to repair a private dam, we at least want a runnable dam as a result. I would prefer a free flowing San Marcos River, but I will settle for a river with runnable dams at every location where we now have unrunnable models - if that's the best we can do.

The next dam downstream is Cumming's Dam. It's the tallest (about 12 feet) and most deadly dam on the upper river. It's so bad that even Mr. Sewell doesn't like it. I have personally helped recover two bodies from the river of persons who have "drowned" at Cumming's Dam. I put drowned in quotes because it's possible that the victims died before their lungs filled up with water. There is so much rebar and gungamunga below that dam that we lost several grappling hooks while dragging for the bodies. From the way the hook hung and the funny stretch we were getting, I would say we were stuck on rebar, but who knows?

Cumming's Dam, unlike Rio Vista, is not a safe dam. The water drops vertically into a deep pool with unknown gungamunga therein. One kayaker may run it with no problem while the next guy could be skewered like a hunk of meat on a sis kabob. In higher water levels a hydraulic forms that can keep a swimmer indefinitely. The problem with everyone running the dam all of the sudden is that novices will get the idea that it's OK and then the next time the river is up (say at 200 cfs) there will be another drowning. The last guy that drowned did so on a Father's Day several years ago. He had his daughter for the weekend and he took her on a little Father's Day outing that Saturday. He proceeded to get drunk, then, once they got to Cumming's Dam (after portaging the canoe) he proceeded to jump off the dam into the boil. He made it the first time, so his daughter begged him to let her jump off with him. They jumped hand in hand. She got washed clear of the hydraulic, he got stuck. Witnesses saw him make it to the top three times and then they never saw him again. He was found the next day (Father's Day) below Pecan Park. I helped find another body who got stuck in the hydraulic years ago. He washed up about a half mile below Cottonseeds Rapids.

Speaking of Cottonseeds, did you know that Cottonseeds and Old Mill Rapids are all the remnants of old dams? Just shows that dams are good for something.

The next dam below Cumming's is Martindale Dam. It's a sloping dam with a bunch of algae growing on it. Occasionally we'll have someone injured while sliding down that dam but deaths are pretty rare. In high water a big stopper forms below the dam and that's where a kayaker was stuck several years ago. He died when the army helicopter that was rescuing him dropped him on the right bank after performing a daring rescue. I was there and got to watch him die.

Next dam is Staples. Can't think of any deaths related to Staples, but I did break a rib there once while portaging.

After that comes Luling Dam. I think there have been some drownings there involving local kids, but I'm sketchy on the details.

Next is Ottine dam where Larry Kendrick the San Marcos Police Chief died several years ago while practicing for the Water Safari. The water was high and the theory is that he didn't think he was at Ottine but at a little rapid upstream of Ottine. Ottine is normally a ten foot drop but at that time it only had a small drop with a huge hydraulic.

Gonzales Dam is next. It's killed several locals as well. One story involved a group of kids in a large raft. It's actually just downstream of the confluence of the San Marcos and Guadalupe Rivers.

Finally, if you want to talk about nasty dams with big hydraulics and difficult portages there's Cuero Dam. It's my favorite dam to hate. But again, it's a long ways below the confluence.

There's even a salt water barrier dam just before Tivoli Bridge, but it isn't even a dam unless the river is real low. Then it can become quite nasty. Nothing like swimming around in a hydraulic with the big gators.

At any rate, there's the whole dam story from San Marcos to the coast. A lot of aging structures that could become a lot of neat rapids. But until then, my advice is to avoid dams (with the exception of Rio Vista) and concentrate on running rapids instead.

Tom Goynes


Water sports are potentially dangerous. You are are are responsible for yourself. Get lessons. Go with a grouop. Know your limits and don't exceed them.

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