About Tideline Marin

I run the Mill Valley to Sausalito path most weeks. This fall I kept reaching Bothin Marsh to find the path under water, with no good way to know beforehand. In late October 2026 the king tides closed Miller Ave by Tam High day after day, flooded Shoreline Hwy at Manzanita, and put the path under water again. The tide tables said one thing, the water said another.

So I built the thing I wanted: a plain answer to "will it be flooded when I get there?" for the spots I actually use.

What it does

• Takes the NOAA tide prediction for San Francisco and adjusts it by how far the real water has been running above or below the prediction over the last 12 hours. That offset fades toward the weekly average over three days.
• Compares that forecast with a level for each spot where water usually shows up, learned from past closures and my own observations, then shifts the timing because each spot floods a little after the San Francisco peak and drains later.
• Shows Clear, Possible or Likely for each spot, the next window in plain words, and a map you can scrub through the next 7 days.

What it does not do

• It does not know about official closures. Police, Caltrans and barricades always win over this site.
• It does not model rain, storm drains or creek flow. Heavy rain at high tide can flood places earlier and deeper.
• It covers three spots for now: Miller Ave at Tam High, Shoreline Hwy at Manzanita, and the path through Bothin Marsh.
• It sends no alerts yet.

These are estimates. Never drive, bike or walk through floodwater. It is often deeper than it looks, and it is salt water.

Contact

If a forecast was wrong, or you saw water somewhere it said Clear, I would love to hear about it: [email protected].