San Francisco Chronicle: Two decades ago, water breached a levee on Tyler Island, 8,800 acres along the northeastern edge of the Sacramento-San Joaquin River Delta, wiping out crops, damaging buildings and nearly destroying the Mello family’s farming business. Steve Mello worries the same thing may happen again – with the approval of state policymakers who are considering whether to save some islands if increasingly fragile levees fail. It’s a familiar scenario for Mello, who has heard proposals in the past to flood …