SCOUR 
 
 AT 
 
 BRIDGES 
 
 What's it all about? 
 
 Stream Stability and Scour Assessment 
 at Bridges in Massachusetts 
 
 A Brief Description of the 
 U.S. Geological Survey Project 
 
 UMASS/ AMHERST 
 
 ■?H/&-sr \ 
 
 Linda P. Warren, 1993 
 
Pier Abutment 
 
 Water Surface 
 
 What is scour? 
 
 River Bottom 
 
 Scour is the hole which forms when 
 sediment (sand and rocks) is washed away 
 from the bottom of a river. Although scour 
 may occur at any time, scour action is 
 especially strong during floods. Swiftly 
 flowing water has more energy than calm 
 water to lift and carry sediment down river. 
 
 Three types of scour affect bridges: 
 
 1 ) Local scour is removal of 
 sediment from around bridge piers or 
 abutments. (Piers are the pillars supporting 
 a bridge. Abutments are the supports at each 
 end of a bridge.) Water flowing past a pier or 
 abutment may scoop out holes in the 
 sediment; these holes are known as scour 
 holes. 
 
 2) Contraction scour is the 
 removal of sediment from the bottom and 
 sides of the river. Contraction scour is caused 
 by an increase in speed of the water as it 
 moves through a bridge opening that is 
 narrower than the natural river channel. 
 
 3) Degradational scour is the 
 general removal of sediment from the river 
 bottom by the flow of the river. This sediment 
 removal and resultant lowering of the river 
 bottom is a natural process, but may remove 
 large amounts of sediment over time. 
 
Why be concerned about scour? 
 
 If sediment or rock on which bridge 
 supports rest is scoured by a river, the bridge 
 could become unsafe for travel. In 1987, the 
 Interstate Highway bridge over Schoharie 
 Creek in New York State collapsed during a 
 flood. After this accident, the Federal 
 Highway Administration required every State 
 to identify highway bridges over water which 
 are likely to have scour problems and to 
 identify bridges where scour is severe. 
 Knowledge of bridge sites where scour is a 
 potential problem will enable the States to 
 monitor and improve conditions at these 
 bridges ahead of time-- before they become 
 dangerous. 
 / 
 
 What is involved in a bridge-site 
 examination? 
 
 A bridge-site examination for scour 
 begins in the office of the Massachusetts 
 Highway Department, where historical 
 engineering information and bridge 
 plans are reviewed. The examiner then 
 visits the bridge site, walking upstream 
 and downstream from the bridge and 
 taking notes on the condition of the 
 river channel. Other characteristics 
 
Whom may I contact for more 
 information? 
 
 For questions concerning the 
 Bridge Scour Program, contact: 
 
 Michael C. Yurewicz, Chief 
 
 Massachusetts-Rhode Island District 
 
 U.S. Geological Survey, Water Resources 
 
 Division 
 
 28 Lord Road, Suite 280 
 
 Marlborough, MA 01752 
 
 Phone: (508) 485-6360 
 
 For questions concerning all other 
 aspects of the bridges in Massachusetts, 
 contact: 
 
 Michael W. Swanson, Chief Engineer 
 
 Massachusetts Highway Department 
 
 10 Park Plaza 
 
 Boston, MA 02116 
 
 Attention: Joseph P. Gill, Bridge Engineer 
 
 Phone contact: 
 
 Paul L. Nardone, 
 
 Bridge Inspection Engineer 
 
 (617) 973-7574 
 
 Special thanks to Mrs. Bisol's 
 
 fifth grade class at the John Greenleaf 
 
 Whittier School in Haverhill, Massachusetts 
 
 for their suggestions and comments regarding 
 
 this publication. 
 
The mission of the Water 
 Resources Division of the U.S. Geological 
 Survey (USGS) includes, in part, 
 identifying potential water-related 
 hazards and determining their causes 
 and character, and providing 
 information used by Federal and State 
 agencies to assess the effects of these 
 hazards on public health, safety, 
 property, and the environment. This 
 mission supports the overall mission of 
 the U.S. Department of the Interior and 
 the U.S. Geological Survey. 
 
 nJdis pamphlet was printed 
 on recycled paper. 
 
 ^Cease recyck. 
 
The mission of the Water 
 Resources Division of the U.S. Geological 
 Survey (USGS) includes, in part, 
 identifying potential water-related 
 hazards and determining their causes 
 and character, and providing 
 information used by Federal and State 
 agencies to assess the effects of these 
 hazards on public health, safety, 
 property, and the environment. This 
 mission supports the overall mission of 
 the U.S. Department of the Interior and 
 the U.S. Geological Survey. 
 
 This pamphlet was printed 
 on recycled paper. 
 
 (Please recycle.