Gauge alerts for whitewater paddlers

The idea

Rain-fed whitewater runs have shelf lives measured in hours: the creek comes up overnight and is gone by Sunday lunch. Paddlers cope by compulsively refreshing USGS gauge pages, and the difference between catching a run and missing the season is often just who looked first. American Whitewater publishes the runnable ranges for thousands of reaches but sends nothing when a gauge enters one.

The wedge is pure alerting done properly: per-run min/max in cfs or feet, rising/falling direction (a rising 500 cfs and a falling 500 cfs are different rivers), and an SMS within 15 minutes of the reading. No content, no community, just the text that gets you loading the boat.

Who pays

The buyer is a kayaker or packrafter with 2,000-plus dollars of boat and kit whose scarce resource is runnable water; 15 dollars a year to never miss a window is the easiest sell in the sport. Stripe subscription, free single email watch as the hook. Distribution: regional paddling Facebook groups and clubs (each has a local gauge everyone obsesses over), r/whitewater, and boater forums; one shared alert screenshot after a classic comes in does the marketing.

MVP scope

• Gauge search with current readings and 7-day sparkline
• Watches with min/max in cfs or gauge height, direction filter, quiet hours
• 15-minute batched polling of the USGS Instantaneous Values API
• SMS and email alerts with debounce and re-arm logic
• PAUSE and STOP SMS handling
• Skip for v1: rainfall forecasting, Canadian and state-only gauges, trip planning, flow predictions, native apps

Build RiverPing, a Next.js web app that does one thing: text paddlers the moment a river gauge enters their runnable window.

Core object is a Watch: a USGS gauge plus a min and max value (user chooses cfs or gauge height, since some runs are quoted in feet), an optional direction filter (alert only while rising, only while falling, or both), and quiet hours. Users find gauges via search by river name or state, backed by the USGS Water Services site list; show each gauge's current reading and a 7-day sparkline before the user commits.

Polling: a scheduled job every 15 minutes pulls instantaneous values for all watched gauges from the USGS Instantaneous Values API (batch gauges into single requests, the API accepts comma-separated site codes). Fire an alert when a reading crosses into the window, respecting direction: compare against the previous reading to classify rising or falling. Debounce: once alerted, do not re-alert for that watch until the gauge leaves the window and re-enters, or 12 hours pass.

Alerts via Twilio SMS and email, message format: river name, reading with units, rising/falling arrow, and a link to the hydrograph. SMS replies STOP handled by Twilio, PAUSE pauses the watch for 7 days.

Pages: Gauge search, My Watches (with live readings), Watch editor, Account/billing.

Auth: magic link. Pricing via Stripe: free tier is 1 watch with email only; 15 dollars per year for unlimited watches and SMS.