This chapter discusses the need for dredging and covers the setting of environmental windows for dredging (i.e., periods when dredging is allowed because of potentially minimal environmental impact), a process that is currently characterized by very conservative estimates that do not take other criteria, such as cost and efficacy, into account. The application of an outranking methodology allows one to see which dredging methodology, in which proposed time period, would be most desirable both for the ecology and for the bankroll.