Climate change is worsening the already significant threat of flooding in California’s farm country, and state officials said Thursday that as much as $30 billion may be needed over three decades to protect the region, an increase from five years ago.

Every five years, flood protection plans are updated for the Central Valley, where about 1.3 million people live at risk in floodplains. State officials released a draft of the latest update that calls for investing in levees, maintenance and multi-benefit projects that recharge aquifers and support wildlife while enhancing flood protection.