San Marcos Mercury | Local News from San Marcos and Hays County, Texas


Wading into a battle that has divided the San Marcos River’s most passionate defenders, the San Marcos City Council is scheduled to begin deliberation tonight on whether to dismantle Cape’s Dam.

Battered by the floods of October 2013 and May 2015, the dam has deteriorated into a indisputable hazard of jagged concrete and rusty rebar. Stretching about 100 feet across the river at the northern tip of Thompson’s Islands, the dam was originally built at least a century ago and, by some accounts, dates to the 1860s.

In a study commissioned by the city, Thomas Hardy, a Texas State University biology professor and the Meadows Center for Water and the Environment’s chief science officer, concluded that the dam’s removal would “reestablish natural current velocities, remove fine sediment accumulation, and restore coarse sediment transport within this reach of the San Marcos River, thus providing improved habitat for vegetation growth and expansion.”

The professor will present his findings to the city council at its regular meeting tonight.

Hardy’s conclusions are accepted by the San Marcos River Foundation and the city’s Parks & Recreation advisory board which has recommended that the council have the dam removed. The municipal government took ownership of the dam and about 20 acres of riverside property — the islands included — as part of a development agreement that allowed construction of The Woods apartment complex nearby.

Meanwhile, a group called Save Thompsons’s Islands led by Olympic kayaker Ben Kvanli is advocating for a restoration of the dam in the mold of Rio Vista Falls, another failing dam upriver that was a transformed into series of manmade rapids in 2006. Kvanli, who owns the Olympic Outdoor Center kayaking school just around the bend from Cape’s Dam, has said rebuilding the structure will enhance the recreational value of the river.


City staff cover memo on Cape’s Dam discussion [pdf]

Hardy study on Cape’s Dam removal [pdf]

Presentation on Cape’s Dam study [pdf]

Supplemental memo on removal of Thompson’s Islands mill race [pdf]


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3 thoughts on “Future of Cape’s Dam, Thompson’s Islands on San Marcos council agenda

  1. Did the City make a decision last night on this?

    P.S.: To comment on: “…rebuilding the structure will enhance the recreational value of the river.” …I’d like to add that improving the recreational value of Stokes Park exposes the need for clean-ups extending to the city limits, at least.

  2. Rob
    The Cape’s Dam presentation and discussion were postponed. It was a long meeting with a full agenda i.e. more than 5.5 hours. They’ll apparently deliberate it when they can do so more deliberately.

  3. I would like to say that as a resident of San Marcos, I have been to Thompson Island plenty of times and I really enjoy it. It would be such a shame for them to take it away.

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