Portable collapsible fluid containment devices are disclosed comprising sidewall support braces that rotate from a collapsed generally horizontal position to a raised generally vertical position and lock into place. The sidewall braces may be attached to at least one sidewall of the containment device, and when raised support the sidewall in a fluid containment configuration. The sidewall braces comprise a base support leg, a sidewall support arm rotatably mounted on the support leg, and a locking tab for holding the sidewall support arm in the generally vertical position.