Cookham Parish Council wrote a Community Flood Plan (pdf, 602kb) back in 2011 based on a template from Windsor and Maidenhead Council and the Environment Agency. It is a long (43 pages) and detailed document.
The information about opening the Causeway was correct at the time of writing in 2011, but is now out of date. New opening times for the causeway have been agreed with Windsor and Maidenhead Council. Community volunteers are needed to help pedestrians cross the Causeway safely.
You can view the document here by scrolling around in the window below. Or you can download it (pdf, 602kb).