B737 FLT CREW ON VISUAL APPROACH TO LEFT RWY IS SWITCHED TO RIGHT RWY BY TOWER AT 1500 FT. FLT CREW DISCOVERS LANDING FLAPS NOT SET AT 800 FT AGL AND LANDS AFTER SELECTING FLAPS 30.

Narrative

LANDING AT ZZZ; WE WERE CLEARED FOR THE VISUAL AND EVENTUALLY CLEARED TO LAND ON RWY XXL. CONDITIONS WERE VMC BUT WINDY WITH GUSTS. OUR REF SPEED WAS 152 KNOTS DUE TO WIND AND WEIGHT. WE HAD CONFIGURED THE PLANE TO GEAR DOWN AND FLAPS 15 AT THIS TIME. BETWEEN 1500 FT AND 1000 FT AGL; WE WERE CLEARED TO LAND ON RWY XXR NOW DUE TRAFFIC STILL ON THE RWY XXL. I WAS THE FLYING PILOT AND STARTED MY TURN FOR THE NEW RUNWAY. THE CAPTAIN DIALED IN THE NEW FREQUENCY FOR THEIR ILS RWY XXR FOR REFERENCE. AROUND 800 FT AGL; WE DISCOVERED THE CONFIGURATION OF THE PLANE AND THE CAPTAIN SELECTED FLAPS 30 AND WE CONTINUED WITH NO OTHER EVENTS. AFTER WE LANDED; WE COULDN'T BELIEVE WE FORGOT THE FLAPS. BUT WITH THE RUNWAY CHANGE DISTRACTION AND THE HIGH REF SPEED; IT DIDN'T CLICK UNTIL WE WERE BELOW THE 1000 FT AGL POINT. WHEN WE GOT TO THE GATE; WE DISCUSSED WHAT HAPPENED AND WERE IN DISBELIEF OF EACH OTHER THAT WE DIDN'T ELECT TO GO AROUND PER SOPS. SOPS ARE CLEAR AND ANY EVENT IN THE FUTURE SHOULD BE COMPLIED WITH AS STATED.SUPPLEMENTAL INFO FROM ACN 778824: WE WERE DOING A VISUAL APPROACH TO RWY XXL AT ZZZ. TOWER SWITCHED US TO RWY XXR AT ABOUT 1500 FT AGL DUE TO TRAFFIC ON THE RUNWAY. TARGET SPEED WAS 152 KNOTS DUE TO WINDS AT ZZZ. FO WAS FLYING CORRECT SPEED AND READY TO CALL FOR FINAL FLAPS WHEN TOWER SWITCHED US TO RWY XXR. I SWITCHED HIS LOC FREQUENCY FOR HIM SO HE WOULD HAVE GLIDESLOPE INFORMATION WITH THE GUSTY WINDS. JUST AFTER THE 1000 FT CALL; THE AIRPLANE GAVE US THE CAUTION; 'TOO LOW FLAPS.' I SELECTED FLAPS 30 AND WE LANDED. WHEN WE GOT TO THE GATE; WE DISCUSSED OUR MISTAKE AND WERE BOTH SURPRISED WE COULD DO SOMETHING SO STUPID. WE ALSO REALIZED WE SHOULD HAVE EXECUTED A GO-AROUND WHEN WE DISCOVERED OUR MISTAKE. DOUBLE CHECK EVERYTHING WHEN OPERATING IN A NON STANDARD ENVIRONMENT (RUNWAY CHANGE AND GUSTY WINDS). CHECKLIST!