Trees can be messy! These look like they could be the flowers of honey locust, Glenditsia triacanthos and you have a bumper crop.

Honey locust have single sex trees with either male or female flowers though there are also some male and female (called perfect) flowers. They appear in early summer, the female flowers on longer, 3 - 4 inch stalks with a cluster of flowers. The male flowers fall singly or on shorter stalks. This happens just once a year and flower production varies each year with weather conditions and some element of tree survival strategy.

It should be over soon!