The California Environmental Quality Act (CEQA) analysis on the Housing Element seemed to just accommodate the growth rather than indicate the negative impacts. Don’t the negative impacts of more housing prevent the City from having to accept more housing?

No. A Housing Element has never been rejected because the environmental impacts were too negative. CEQA analysis generally notes what environmental impacts there are, then attempts to identify how those impacts can be mitigated. While concerns like increased traffic, wildfires, or water availability are valid, and the City of Yorba Linda is working to address these impacts, the negative consequences of these issues will not provide a reason for the City to not fulfill its RHNA requirements.