Coastal flood warning: what San Diego’s high tides mean for your home this week

The National Weather Service in San Diego has stepped up its coastal alert. Two weeks ago it was a Beach Hazards Statement. Now it’s a Coastal Flood Warning for the San Diego County coast. The warning runs until 1 p.m. Thursday, and the trouble comes in the late morning, when each day’s high tide peaks.

Forecasters say the ocean keeps rising higher than the tide tables predict. If you live, park or own property near the bay or the beach, here’s what the warning means and what to do before Wednesday’s and Thursday’s high tides.

What the warning says

NWS San Diego’s latest update, issued Monday afternoon, covers the coastal areas of San Diego and Orange counties. It lists these impacts:

• Numerous roads may be closed.
• Low-lying property, including homes, businesses and some critical infrastructure, will be inundated.
• Some shoreline erosion will occur in the late mornings.

The key detail is that observed high tides are 1.5 to 1.7 feet above the astronomical tide predictions. Tide tables are based on the moon and sun. They don’t account for whatever is pushing extra water toward the coast this fall, so the water is ending up well above where the charts say it should.

Warning vs. advisory: why the upgrade matters

The National Weather Service uses a three-tier system. A watch means flooding with significant impacts is possible. A warning is more serious. NWS issues one when flooding that poses a serious threat to life and property is occurring, imminent or highly likely. The Beach Hazards Statement two weeks ago warned of minor flooding and erosion. This week’s alert is a full warning.

When to watch the water

On San Diego Bay, NOAA predicts these morning high tides for the rest of the warning (Tuesday’s peaked at 9:51 a.m., predicted at 7.1 feet):

• Wednesday, Oct. 28: 10:29 a.m., 7.0 feet
• Thursday, Oct. 29: 11:13 a.m., 6.7 feet

These are predictions for NOAA’s San Diego Bay station, measured from the average lower low water line. Other spots along the coast will run a little earlier or later. If tides keep running 1.5 to 1.7 feet above predictions, as NWS has observed, Wednesday’s 7.0-foot tide would arrive at roughly 8.5 to 8.7 feet. That’s simple arithmetic, not an official forecast, but it shows why the warning was issued.

The nighttime high tides are much lower, around 4 feet. The hours to watch are mid-morning to early afternoon.

Expect waves to run farther up the beach than usual, and stay well back from the water. — NWS San Diego

What to do at home

The NWS warning tells people in the affected area to take steps to protect property that tends to flood. If you’ve seen water reach your street, driveway or garage before, these steps help:

• Move things up and out. Get cars, bikes, tools and anything stored on the floor of a garage or ground-floor room out of the water’s path before the late-morning tide.
• Clear the path for drainage. Keep storm drains and yard drains free of leaves and debris so the water that does get in can drain out. California’s Office of Emergency Services recommends this before any flood.
• Have sandbags and tarps ready. The City of San Diego offers empty sandbags at 11 recreation centers, including Pacific Beach Rec Center and Robb Field in Ocean Beach. The limit is 10 bags per household or business, and you bring your own sand. Other coastal cities, including Coronado, Imperial Beach, Oceanside, Encinitas, Del Mar and Solana Beach, have their own sites, listed on AlertSanDiego’s sandbag page. Call ahead to make sure a site still has supplies. City details are on the city’s storm preparedness page.
• Check your coverage. Standard homeowners insurance doesn’t cover flood damage, Cal OES notes.

What to do on the road and at the beach

• Don’t drive around barricades or through water of unknown depth.
• Stay off jetties and seawalls during high tide.
• Avoid the beach around high tide. Waves will run farther up the sand than usual.
• Build in extra time for coastal drives in the late morning, since NWS says numerous roads may close.

Two weeks ago, we explained what the earlier Beach Hazards Statement meant and why the gauge readings kept topping the tide tables. That pattern is still going, and this week the water is higher. For the longer view, see what El Niño means for San Diego’s beaches and our pre-storm home checklist.