Scour design guidance in the United States allows the use of riprap as a countermeasure to reduce the risk/implications of scour for existing bridges, but does not allow its use for new bridges. Rather, the foundation of new bridges must be placed "at such a depth that the structural stability will not be at risk with maximum scour." This approach may have significant implications with respect to the design and cost of the bridge structure. In contrast, riprap is generally accepted as a permanent countermeasure against scour for bridges in Europe and in Canada. In addition, thousands of "rubblemound" structures have been designed and implemented in the field of coastal engineering over the past 150 years, including breakwaters (to protect harbor and other marine facilities), revetments, embankments and dams (to prevent erosion) and scour protection (for coastal structures, marine pipelines, etc.). Some of this experience can be applied to the design of scour protection for bridges. Baird has recently undertaken scour assessments for two large bridges in Eastern Canada, including the St. John River Bridge on the Trans-Canada Highway in New Brunswick and the Confederation Bridge across the Northumberland Strait between New Brunswick and Prince Edward Island. Extensive analyses were undertaken for both projects in order to estimate potential scour depths, assess alternative scour countermeasures, and design effective scour protection systems. Physical modeling was undertaken in order to design riprap scour pads to prevent scour around the piers while also remaining stable under the extreme design conditions. This paper provides an overview of these two projects and scour-related issues, focusing on the investigations undertaken to develop designs for riprap scour pads to provide permanent protection against scour. In particular, it is concluded that a carefully designed physical model investigation provides an accurate and cost-effective tool to assess/quantify the performance of riprap scour protection systems under extreme flow conditions, thereby allowing the design of permanent scour protection systems that may result in significant cost savings for many bridge projects.