The second unreasonably broad hypothetical in one week - 12 foot floods outside of floodplains, now where to go for self-sustaining harvest areas when those areas are massively complicated by overpopulation, ownership, and rules of entry (squatting). But if we can ignore the illogic of a 12 foot flood, I'll ignore the hard part of this scenario too. I would go east of the Cascades, to the Columbia River basin, where native americans lived in reasonably peaceful populations for 10,000 years migrating between the river for salmon, uplands for camas croots and berries and to hunt deer, and most recently over to the prairies to hunt buffalo. Migration patterns were stable, tribally based, which shows that people could survive in any of several different microclimates, but most likely they moved between them freely and seasonally. It could be a good life. I, personally, would die of starvation within 3 months, but what the hell. Its just a scenario.