The San Diego River's flood history and the gauge near Santee

What is the Mast Boulevard gauge, and why does it matter?

The Mast Boulevard gauge is a measuring point on the San Diego River near Santee. It is the reading the public can follow, and its flood stage is the line against which a rise is judged.

A river gauge records the height of the water at one point, and the record is kept so that rises can be compared over time. For this area the Mast Boulevard gauge is the reference that the flood record uses. A reading above the flood stage means the river is over the level at which flooding is recorded at that point.

The gauge does not tell you the flood risk of a particular street or building. It shows the river's level at its own point, and the effect on a building depends on the ground, the drainage and how close the building sits to the water. Use the gauge as the public reference for the river, and use a local assessment for your property.

What happened when the river rose in January 2023?

On January 16, 2023 the river reached 12.8 feet at the gauge, above its 10-foot flood stage. The National Weather Service's yearly summary records about a dozen swift-water rescues that winter, and a potent storm moved into the region on January 31.

The rise is the most recent large event on the gauge in the sources this guide relies on. A reading above flood stage is serious because the water spreads beyond the banks, and the speed of the current makes rescue difficult. The summary records the rescue count as about a dozen, and that figure comes from one National Weather Service summary.

The yearly summary also places a potent storm moving into the region on January 31, late in the month. The sources do not set out the full sequence of that storm, and this guide does not reconstruct it. The point for a homeowner or a business owner is that a rise of this size is a reason to plan for water in rooms that do not usually see it.

What was the 1995 overflow into Santee?

The National Weather Service's compilation of significant weather events records a 1995 overflow of the San Diego River into Santee. The compilation flags that date for checking, so this guide treats the event as a past record without relying on the exact date.

A river that overflows into a city is the same kind of event as the 2023 rise, though the sources give fewer details for 1995. What the record shows is that the river has reached Santee before, and that the risk is not limited to one year.

Because the date is flagged for checking, the public version of this history should be read as a record of a past overflow, not as a schedule. The National Weather Service compilation is the place to check the detail.

Why does a river flood differ from a broken pipe?

River water has been in contact with soil, roads and debris, so it is handled as contaminated. A broken pipe usually releases clean water, and the removal rules for the two are different.

Silt from a river settles into carpet pad, the bottom of walls and the gaps in flooring. It cannot always be removed by drying alone, so the scope often removes porous material that holds silt. A clean supply-line leak is usually dried in place where the material reads dry.

The crew sets the category on arrival and explains it to the owner. If the category changes, because the water is found to have come from a different source, the scope changes with it and the reason is written down.

How should a homeowner use the gauge reading?

Use the gauge reading as a sign that the river is high, and treat a reading above flood stage as a reason to move valuables and check the shut-offs. The reading does not tell you whether your building will flood.

The most useful step is to plan before the water arrives. Move valuables to a higher room, keep the shut-offs and the panel clearly known, and keep the number of the line handy. A plan made before a rise is easier to carry out than one made in the water.

Do not walk into moving water or onto a levee or bank to look at a flood. Stay away from fast-moving water, and follow the instructions of local officials when they are given.

Check the National Weather Service forecasts and any watches or warnings for the county during a wet spell, since they give more notice than a gauge reading alone. A watch is a time to prepare and a warning is a time to act, and the difference matters for what a household does with the next hour.

What should a building owner keep on file?

Keep dated photographs of each room, a record of the valuables and their location, and the name of the insurer and the policy number. Keep the scope and the readings from any past water loss with the same file.

A dated record makes a later claim easier to prove. Photograph the rooms in good light, and note the height of any high-water mark you can see. A simple written list of what is stored where is also useful, since it shows what was lost.

Keep the copies somewhere that will not flood. A cloud copy or a copy kept at a relative's house is safer than one kept in the same room as the valuables.

Where can the flood record be checked?

The National Weather Service's San Diego office publishes the yearly climate summary and the compilation of significant events that this guide draws on. Those are the primary sources to check for the dates and figures given here.

The yearly summary for 2023 and the historical compilation are both published by the National Weather Service, and both are linked in the sources below. The compilation includes older events whose dates are flagged for checking, so read those entries with that in mind.

For a particular property, ask the local office that covers the address about any mapped flood zone or local drainage issue, and ask your insurer what it requires. This guide shows the river record, and it does not map any individual building.

What should you do in the first hour of a river flood?

Move people to higher ground, keep away from moving water and electrical equipment, and call the line for the water that is already inside. Do not go to the river bank or into a flooded road to look at the flood.

The first hour is about people before property. If water is rising near the building, move to a higher room or floor by a route that keeps you out of standing water. If the way out is blocked, stay in the highest safe room, call emergency services and say where you are. Do not wait for the water to reach the outlets before deciding to move.

Once everyone is safe, turn off power to any area you cannot reach dry, only if you can do so safely, and call the line. Photograph the water's height on the walls if you can do it without entering the water. Those marks help the crew and the insurer later, and they show how far the river reached on that day.