  Compound flooding, where the combination or successive occurrence of two or
more flood drivers leads to an extreme impact, can greatly exacerbate the
adverse consequences associated with flooding in coastal regions. This paper
reviews the practices and trends in coastal compound flood research
methodologies and applications, as well as synthesizes key findings at regional
and global scales. Systematic review is employed to construct a literature
database of 271 studies relevant to compound flood hazards in a coastal
context. This review explores the types of compound flood events, their
mechanistic processes, and synthesizes the definitions and terms exhibited
throughout the literature. Considered in the review are six flood drivers
(fluvial, pluvial, coastal, groundwater, damming/dam failure, and tsunami) and
five precursor events and environmental conditions (soil moisture, snow,
temp/heat, fire, and drought). Furthermore, this review summarizes the trends
in research methodology, examines the wide range of study applications, and
considers the influences of climate change and urban environments. Finally,
this review highlights the knowledge gaps in compound flood research and
discusses the implications of review findings on future practices. Our five
recommendations for future compound flood research are to: 1) adopt consistent
definitions, terminology, and approaches; 2) expand the geographic coverage of
research; 3) pursue more inter-comparison projects; 4) develop modelling
frameworks that better couple dynamic earth systems; and 5) design urban and
coastal infrastructure with compound flooding in mind. We hope this review will
help to enhance understanding of compound flooding, guide areas for future
research focus, and close knowledge gaps.
