Artificial alteration of channel sides and/or bottom. Artificially armoring banks, lining channels with concrete, and fixing channels in place can all affect both aquatic and riparian/floodplain ecosystems.

The maximum flood that can be experienced without exceeding some amount (e.g., $10 million) in damages. Resilience will increase with improved flows access to floodplains and removal of infrastructure from floodplains.

Expected annualized damage for flood risk. The projected cost of repair and replacement can be modeled for different flooding scenarios.

Proportion of floodplain that is protected from development that is incompatible with flooding. Conserving and restoring floodplains can have profound effects on the risk and effects of flooding.

Extent of floodplain restoration and connection between channel and floodplain. Both the absolute amount of protection and restoration and the proportion of the historic area are informative.

Flow pattern variability / alteration (both important seasonally and annually). Ecosystems depend on natural flow patterns and variability. High flows are needed to move sediment and re-work riparian and floodplain areas.

Flood occurrence is the number of floods recorded from 1985 to 2011. The indicator was used by the World Resources Institute in the Aqueduct 2.0 project.

Cumulative hydrostatic force on levees and other flood-control structures. This is a measure of the calculated force that rivers in flood put on segments of levee, which can highlight areas vulnerable to failure under certain flood conditions.

Proportion of watershed covered by impenetrable materials such as roads, parking lots, and buildings preventing water from leaching directly into the soil. The greater the proportion of watershed with impervious surfaces, the greater the likelihood of geomorphic processes and conditions being degraded due primarily to modifications of stormwater runoff dynamics.

Building standard and cost of maintaining levees/assessed value of the land use they protect. This ratio of benefit to cost helps us understand levees are the most important in a system.