SLOPES IV – Structure Span OHW ACW Functional Floodplain Span (FFS) Paul R. Wirfs, P.E. Oregon Department of Transportation Engineering & Asset Management Unit Manager

SLOPES IV – Structure Span Bridges and Culverts Good Engineering Judgment Streamlined Permitting Option Early Evaluation & Communication

SLOPES III Total Scour Elevation Active Channel Width Total Scour Depth

BRIDGE SCOUR

Total Scour at a Bridge Total Scour Elevation Total Scour Depth Functional Floodplain Span (FFS)

Key Terms General Scour Depth ACW Bank Full Width Top of Bank General Scour Elevation OHW Thalweg

Functional Floodplain Span Single Span Structure –1.5 x Active Channel Width Multi-Span Structure –2.2 x Active Channel Width

General Scour Prism General Scour Depth OHW ACW Functional Floodplain Span (FFS) AB FFS = ACW + A + B General Scour Prism

Functional Floodplain Span Single Span Structure –FFS = 1.5 x ACW = ACW + A + B –A+B = 0.5 x ACW Multi-Span Structure –FFS = 2.2 x ACW = ACW + A + B –A+B = 1.2 x ACW

Bridge Abutment Protection Required Because: –Abutment Scour not considered –Channel Migration –Foundation on Erodible Materials

GEOENVIRONMENTAL/ ftp://ftp.odot.state.or.us/SLOPES_IV Paul R. Wirfs, P.E. Oregon Department of Transportation Engineering & Asset Management Unit Manager