From the Pew Trusts, this report (11 pages) on disaster mitigation. Natural Disaster Mitigation Spending Not Comprehensively Tracked. Most federal funding to help states manage cost growth is available only after an incident. Here is the concluding paragraph:

Because the federal government and state do not know how much they spend on mitigation in total, they lack the information to accurate compare proactive investments with post-disaster response and recovery Expenditures. All levels of government need a more comprehensive understanding of federal and state investment in order to better target funding to help manage the growing costs of catastrophic events.

FEMA used to have a program called Project Impact, which made money available for mitigation prior to a disaster. But the G..W. Bush administration killed the program. It is truly painful to see lessons forgotten or ignored.

Update: for those not familiar with Project Impact, which was notable and effective during its short life, I suggest you use Google Scholar with the search term “FEMA and Project Impact.” There you will find several studies and articles. See especially the study done by the Univ. of Delaware.