Size – yes; a timber vessel that large can’t be structurally seaworthy, but timber-framed and a reed hull could be if the frame was allowed to flex.
A year? Ordinary-sized reed boats could last for a number of years, so presumably a large vessel could as well.
And both become far more plausible in the proposed regional flood since the storm waves wouldn’t be nearly as large – open-sea storm waves can reach or top fifty meters high; in that regional basin I expect twenty meters would be the maximum.