JIM STEWART showed me how small of a debris field is left when a Whipple bowstring iron bridge falls. The wood usually floats away, and most of the iron usually separates and sinks. So what is left? See the following three pics for the large Whittlesey Road (Whipple bowstring) Bridge that collapsed, which was spanning the Black River at Whittlesey Road, Lyons Falls, Lewis County, NY..
https://www.loc.gov/pictures/item/ny1768.photos.351133p/resource/
https://www.loc.gov/pictures/item/ny1768.photos.351134p/resource/
https://www.loc.gov/pictures/item/ny1768.photos.351135p/resource/