San Marcos

Rio Vista Park was once the site of a sloping 8-foot low-head dam with a chute in the middle that created a play hole at certain levels.  The dam, which was constructed in 1904, was badly damaged in the flood of 1998 and became structurally unsound, and in early 2006, it was extensively renovated and turned into a whitewater park with artificial rapids.  The new whitewater park, which opened on May 25, 2006, extended the 8-foot drop over three drops, spaced about 30 yards apart.  In addition to their recreational value, the second and third drops reduce the turbulence and velocity of the water coming over the original dam (the top drop), which further protects that structure.

The top drop (about 4') is the steepest and largest, and its behavior varies with the river level:

• Low flows (generally < 150 cfs):  All of the river flow is funneled into a single one-boat-wide slide, which creates a surfable wave at the bottom.  The wave is more green and has less well-defined shoulders;  it is thus popular with river boarders.  It is front-surfable by kayakers, but a certain amount of skill is required to stay on it, unless a wave shaper is used.
• Medium flows (generally 150-200 cfs):  The wave is in a transitional state.  At 170 cfs, it is known to form a green tongue only on surfer's right but more of a shoulder on surfer's left, thus requiring the surfer to spin.
• Medium-high flows (generally 200-250 cfs):  Generally considered to be the optimal level for kayakers.  Sufficient water is flowing over the rest of the dam to build good shoulders around the wave and a tall, fluffy pile behind it.  The wave easily gives up spins but can be front-surfed as well.
• High flows (generally > 250 cfs):  The wave becomes more of a wave-hole and is not as forgiving or predictable.
• Very

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