B737-700
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 301; Flight Crew Type 26400
Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Illness / Injury; Inflight Event / Encounter Weather / Turbulence
General Flight Cancelled / Delayed; General Maintenance Action; General Physical Injury / Incapacitation
Weather
At the top of descent; we began to encounter turbulence so I instructed the flight attendants to take a seat via the PA. As the descent progressed I talked to the flight attendants via intercom and confirmed they were seated but that their galleys were not secure. I told them to stay seated and if we found a better ride I'd let them get up to secure their galleys. The ride; by that point was light to moderate turbulence. Passing about 20;000 ft. the ride improved dramatically; mostly smooth. The ATIS for ONT showed light winds from the west at about 5 knots. The winds at our altitude were out of the north at about 30 knots. Because we were on the upwind side of the mountains to the north of ZZZ; I assumed; at most; we'd start picking up light occasional moderate turbulence at around 10;000 ft.; thus giving the flight attendants a window to secure their galleys. I let the flight attendants know so they could close up their galleys. Just below 15;000 ft.; we encountered a sudden pocket of severe turbulence followed by continuous moderate turbulence until about 1;000 ft. AGL at which point we flew into the light westerly winds. Immediately after the severe encounter I made a PA instructing the flight attendants to take a seat. As the First Officer flew; I notified ATC and Dispatch via ACARS. I then called the flight attendants to see if they were ok and was informed there was at least one that was injured.I told them to stay seated and that I would have EMTs (Emergency Medical Technicians) meet the flight to check all three of them. I arranged this with a radio call to ZZZ Operations. The landing was uneventful. EMTs meet the aircraft and evaluated all three flight attendants. Two said they were fine and continued on to ZZZ1. The third one was transported to a local hospital for further evaluation. Dispatch; the Supervisor on Duty; and Maintenance Control were notified via phone. A logbook entry was made for a severe turbulence encounter. The aircraft was inspected and signed off.Given the conditions at the time; I did not expect anything close to severe turbulence. Conditions had not developed yet on the surface; and the winds at our altitude were not sufficient strength to raise concern of much greater than light turbulence. The thought was they could quickly stow their galleys and sit down. But that plan didn't work. I should have just left them in their seats and helped clean up the mess that would have resulted on the ground.
B737 Captain reported severe turbulence on approach that resulted in a flight attendant injury.