This chapter focuses on how urban development relates to riverine flood risk. It begins with an overview of flooding and related riverine processes (e.g., sediment transport, floodplain formation, channel migration). It then presents the urban development and flood histories of Vienna (Austria) on the Danube and Calgary (Canada) on the Bow River, including the latter’s 2013 flood disaster. The cases are assessed and compared using the Urban Risk Dynamics framework. Vienna and Calgary demonstrate several key themes, including the “levee effect.” Each city’s relationship with the river has been one of technological control, intensifying over time. During periods of major population growth, flood protection investments are made that allow the city to expand into hazard lands. Once set in motion, the reliance on technology for flood protection becomes self-reinforcing, difficult to reverse as more of the city comes to depend on it. Over time, there is a loss of collective memory about flood risk. The role of government becomes increasingly important. Disaster events lead to learning and adaptation but do not fundamentally alter processes of urban development that give rise to risk.

This chapter focuses on how urban development relates to coastal flood risk. It begins with key concepts related to coastal geomorphology and flooding in river deltas and estuaries (e.g., processes of landscape formation, protective benefit of wetlands, storm surge, human impacts on coastlines). It then presents the urban development and flood histories of New Orleans (including Hurricane Katrina) and New York City (including Hurricane Sandy). The cases are assessed and compared using the Urban Risk Dynamics framework. Both demonstrate how urbanization in coastal cities often entails extensive loss of wetlands, construction of navigational waterways that inadvertently funnel storm surge, and floodplain expansion through land subsidence or building out the waterfront. Urban expansion into more hazardous lands may be intentionally enabled through construction of flood protection structures. Generally, the least economically valuable land was occupied by the most socially vulnerable populations. Catastrophic events like Hurricanes Katrina and Sandy spur mitigation but reinforce ongoing urbanization trends. Lower density areas, however, provide opportunities for strategic retreat.