The 23 year old Canberra cycling star has capped off her season by amassing 925 points to win over current world champion, Mariana Pajon (COL) with 760 points.
In the fifth and final round in Chula Vista, California, Buchanan scraped through to make the final finishing in second place on the tough USA Olympic training track. The race was won by Mariana Pajon (COL) with Alise Post (US) claiming third. Buchanan had previously won the overall series in 2012.
"My main focus today was trying to keep things simple," said Buchanan. "I just needed to go through and do what I do best."
After winning two world cups early in the season Buchanan had challenges in two others. Today's second place saw her on the podium again.
"My main focus was to podium at every world cup. In Holland I just missed out with a photo finish and was struggling in Argentina and made seventh. But now I'm thrilled to be back up there," said Buchanan.
"I am pretty tired but I am relieved. It's always good to finish that final race on a high."
In the men's final race it was current world champion, Sam Willoughby from Adelaide showing his form to take the win. USA rider, Nicholas Long claimed second with Carlos Alberto Ramirez Yepez (COL) in third.
After the leading world cup series elite men riders crashed in the final
stages of the race, the overall BMX World Cup Supercross lead was
eventually taken by Liam Phillips (GBR). Also crashing was Adelaide's
Anthony Dean however he retained second position overall just 100 points
The wins will assist Australia with Olympic qualifying points in the lead up to the 2016 Rio de Janeiro Olympics.