Wash-Crossing Decision Flow

Why this is a decision path and not a calculator

Every other tool on this site answers a question with a number. This one cannot, because the number that would answer it (the depth of the water across the road in front of you) is not knowable from a webpage, and is barely knowable from the driver's seat. What is knowable is the situation you are in, and the situation determines the answer more reliably than the depth does. Somebody on foot beside a running wash and somebody in a car looking at the same water are in different amounts of danger, and the guidance for each is different.

So the four questions are asked in the order the situation unfolds, and the tool refuses to ask the later ones when the earlier ones have already settled it. If you are on foot, the answer is the same whatever the depth is, and asking you to estimate it would only invite you to talk yourself into a number.

Depth is the wrong thing to judge, and everybody judges it

Standing water at a desert crossing is opaque. It carries sediment, it hides the surface beneath it, and the surface may not be there. A single flow can scour the pavement out from under a crossing and leave nothing at the waterline to suggest it. That is why the tool treats "I cannot tell" as an answer rather than as a gap: at a wash crossing, not being able to tell is the normal condition, and it is a reason rather than an excuse.

The same goes for movement. Every official figure on this page is about moving water. Water that looks still at the near edge of a crossing can be running hard at the far edge, and a wash that was dry this morning can be bank to bank ten minutes after a storm you neither saw nor heard.

What to do when published figures do not agree

Three numbers are in circulation for what water does to a car, and they come from two agencies. The National Weather Service's national Turn Around, Don't Drown campaign says 12 inches of rushing water carries away most cars, and 2 feet carries away SUVs and trucks. The Weather Service's own Phoenix office, writing about this valley, says it takes about one to two feet of water to float most vehicles, including SUVs. Maricopa County says two feet of water can float away your car.

It is tempting to present that as a tidy single answer, and this page deliberately does not. Read as a range rather than as three claims, the figures are closer to agreeing than they first appear: the floor is one foot, the ceiling is two, and only the lowest number matters when you are deciding whether to drive into something. Each agency is also describing a slightly different thing. The national campaign draws on the whole national record for when moving water takes control of a vehicle. The Phoenix office is writing about the low-water crossings in this county, where the flows are short and violent and the audience is people who have driven through shallow water before.

So the rule the page applies is the one that works when sources differ: plan by the lowest published figure. If you are covered at 12 inches you are covered at 2 feet. And the disagreement turns out not to matter very much in practice, because it only matters to somebody looking for a depth that is safe to cross, and no agency publishes one at any depth.

The law, and the two things about it that get reported wrong

A.R.S. § 28-910 is called the Stupid Motorist Law in every news story that mentions it. That is a nickname. The statute's own title is "Liability for emergency responses in flood areas; definitions", and it is a civil liability provision, not a criminal one.

The first thing that gets reported wrong is what it does. It creates no offence. Subsection A makes a driver liable for the expenses of an emergency response after operating a vehicle on a public street or highway that is temporarily under water and barricaded because of flooding. Subsection B attaches the same liability to somebody convicted under § 28-693, which is reckless driving. The liability follows an offence that already exists; the section does not add one.

The second is the size of it. The cap is real (the expenses "shall not exceed two thousand dollars for a single incident") but it is a cap on the rescue bill and nothing else. The same language makes the liability additional to any other liability, so it does not limit what the vehicle cost, what an injury cost, or what happens to your insurance. Subsection D expressly allows a policy to exclude coverage for this liability, which means the $2,000 may be the smallest number in the whole event.

What the section does not say is anything about depth, or about whether the water was moving. The fact it turns on is the barricade. An unbarricaded crossing is not addressed by it, which is a statement about the statute and not about whether you should drive through it.

Why a low-water crossing is the dangerous kind

A low-water crossing is a road that dips through a wash, built to be driven over when the wash is dry and to be submerged when it is not. It is not a bridge and it is not a mistake. Bridging every wash on every rural road in Maricopa County would cost many times what the crossings cost, to cross water that is not there most of the year.

The consequence of that trade is worth being explicit about. A crossing is designed to be overtopped, so water across one is not a sign that something has gone wrong; it is the crossing doing its job. There are no rails to stop anything the water carries and usually no depth gauge. The National Weather Service's Phoenix office singles low-water crossings out when it talks about where Arizona flood deaths happen, and this tool exists mainly because that is where people meet them.

What the page will not do

It will not tell you that a depth is safe, because no agency it draws on says that about any depth. It will not advise you on your own legal position. The statute is quoted and explained, and applying it to a particular set of facts is a job for a lawyer, an insurer or a court. And it will not tell you what to do about water inside a building, which is a different problem with its own guidance and its own risks, starting with the electrical panel.

What it will do is put the right answer in front of you before the two minutes of reasoning that people do at the edge of a flooded crossing, which is the two minutes when the decision actually gets made. The four questions produce 96 possible combinations and 7 distinct answers, and every one of them is some version of the same advice: stop, turn around, and take the long way.