Flood Concepts
A collection of practical guides that explain flood topics that are often misunderstood in policy and public discussions.
This collection explains flood topics that are often misunderstood in policy and public discussions, including flood probability, river behavior, floodplains, runoff, levees, and the difference between hazard and risk.
Use these guides to support briefings, planning conversations, land-use discussions, infrastructure decisions, and clearer communication about flood-related issues.
Flood Concept Guides
Browse the collections of plain-language guides that support planning, communication, and resilience discussions.
What a 100-Year Flood Actually Means
Explains the concept of a 100-year flood and how it refers to annual probability, not a once-per-century schedule.
What Bankfull Flow Is and Why Rivers Spill Over
Describes what bankfull flow and overbank flooding are, and why rivers naturally spill onto floodplains.
Why Floodplains Exist
Explores how floodplains, which are natural parts of river systems, form over time as rivers overflow, slow down, deposit sediment, and shift across the landscape.
How Upstream Land Use Changes Downstream Flooding
Shows how upstream land use can change runoff, sediment movement, and flood peaks downstream.
Why Pavement Changes Runoff
Breaks down how pavement and other impervious surfaces reduce infiltration, speed runoff, and can increase flood peaks downstream.
Why Flood Depth Is Not the Whole Story
Discusses why flood impacts depend on more than water depth alone.
What Levees Do and Do Not Do
Clarifies how levees can reduce some flood impacts but do not eliminate flood risk.
Why Flood Risk Is Not the Same as Flood Hazard
Walks through the differences between flood hazard, exposure, vulnerability, and risk.
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