Cascading effects of infrastructure failures from terrorist attacks or natural hazards can greatly increase the magnitude of impacts from a failure of any given infrastructure. Interdependencies among infrastructure sectors in part drive these effects. Capturing how interdependencies operate and heighten impacts to develop procedures and policies to improve recovery is less well understood. This paper first presents an accounting system to identify where interdependencies are likely to occur. Second, given interdependencies, ways to portray vulnerabilities from interdependencies and estimate magnitude with qualitative or integer scales are presented from prior research and event databases. The methodology to quantify interdependencies and associated cascades builds on work on electric power outages and impacts they had on other infrastructure, such as oil and natural gas, electricity, transportation, and water. The method can be used to analyze connections between restoration times and types of interconnections failed and alternative technologies to reduce impacts of cascades.