Minor Flooding — Within 6 hours after heavy rain, small streams, creeks, canals, and drainage ditches become swollen and overflow in a few places. In flatter terrain, quick ponding of water occurs around low-lying spots, especially in historically vulnerable locations. In urban places, quick ponding of water occurs at certain underpasses or poor drainage spots, especially in historically vulnerable locations. Storm drains and retention ponds become near-full and begin to overflow in a few places. In mountain areas, runoff moves down the valley and is becoming a concern, especially in river valleys. Flood waters generally affect a few buildings and roads.

Moderate Flooding — Within 6 hours after heavy rain, rivers and tributaries become swollen and may begin to overspill their banks in a few places, especially in historically vulnerable locations. Small streams, creeks, canals, and drainage ditches overflow. Normally dry gullies or dry creek beds become alive. In flatter terrain, expanded areas of rapid inundation occur around low-lying spots covering several secondary roads. In urban places, expanded areas of rapid inundation occur at several underpasses or poor drainage spots, with some streets and parking lots taking on moving water. Storm drains and retention ponds overflow. In mountain areas, considerable runoff moves fast down the valley washing out some roads, especially in river valleys. Hillsides vulnerable to erosion become a concern for mudslides. Flood waters generally affect several buildings and roads.

Major Flooding — Within 6 hours after heavy rain, rivers and tributaries overflow their banks in several places. Small streams, creeks, canals, and drainage ditches become dangerous rivers. Normally dry gullies or dry creek beds become alive with dangerous and fast moving water. In flatter terrain, extensive inundation occurs covering both primary and secondary roads. In urban places, widespread inundation with streets and parking lots becoming rivers of moving water. In mountain areas, destructive runoff moves fast down the valley washing out everything in its path, especially in river valleys. Hillsides vulnerable to erosion give way to mudslides. Flood waters generally affect many buildings and roads.