The Floristic Quality Index (FQI) was developed for coastal Louisiana, similarly to other regions of the U.S., to determine the quality of a wetland based on its species composition. The FQI is a score from 0 – 100 that can be calculated at various spatial scales including CRMS site, project, hydrologic basin or coastwide. First, each plant species occurring in Louisiana coastal wetlands was assigned a Coefficient of Conservatism (CC) score by a group of Louisiana coastal vegetation experts. A smaller panel of Louisiana coastal vegetation experts compiled and finalized the scores from the larger group. The CC score is based on a species’ tolerance to disturbance and fidelity to a habitat. Invasive plant species were assigned a CC score of 0; plants that are opportunistic users of disturbed sites were assigned a score of 1 – 3; plants that occur primarily in less vigorous coastal wetlands were assigned a score of 4 – 6; plants common in vigorous coastal wetland communities were assigned a score of 7 or 8; and plants that are dominants in vigorous coastal wetland communities were assigned a score of 9 or 10. Since the CRMS site data include percentage cover data, the panel decided to weigh CC scores based on abundance in the FQI for Louisiana coastal wetlands using the following formulas:

FQI_t = (∑ (cover_it x CC_i) / 100) x 10

where sum of species covers at time t is less than or equal to 100; cover_it = percent cover for species i at a vegetation station within a CRMS site at time t; and CC_i = Coefficient of Conservatism for species i. Individual station level FQI scores are averaged to obtain the site level FQI score.

Accordingly, where the sum of species covers at a CRMS vegetation station at time t is greater than 100, we use the formula:

FQI_t = (∑ (cover_it x CC_i) / sum of species cover_t) x 10

Here, species cover_t refers to the cumulative species cover by vegetation station (i.e., > 100%).

The Hydrologic Index (HI) jointly assesses the suitability of two critical aspects of wetland hydrology, average salinity and percent time flooded, in maximizing vegetation primary productivity for the 5 different marsh classifications in coastal Louisiana (swamp, fresh, intermediate, brackish, and saline). The index score ranges from 0 - 100, and the score corresponds to the percent of maximum vegetation productivity expected to occur if the separate effects of salinity and inundation on productivity interact in a multiplicative fashion, according to the following formula:

HI = fld x sal

where fld is the percent maximum productivity attributable to percent time flooded, and sal is the percent maximum productivity attributable to the average annual salinity. Relationships describing how percent maximum productivity varies with salinity and percent time flooded were taken from the Habitat Switching Module of the LCA ecosystem restoration study (U.S. Army Corps of Engineers 2004).

The HI is calculated for a given water year, which begins October 1 and ends the following September 30.

The SVI model assesses the submergence vulnerability of a site based on the 5-year projection of its relative position within the hydrologic frame. Both wetland surface elevation and water levels (based on at least 5 years of data) are projected 5 years into the future. Wetland elevation is projected using surface elevation change rates, and water levels are projected using eustatic sea-level rise rates. The position of the projected wetland relative to the distribution of projected water levels determines the SVI score. A site is scored (0-100) according to the position of the future wetland elevation within the distribution of future water levels using the following equation:

P_n= 100/N * (n-1/2)

where n is the rank of the projected wetland elevation within the projected distribution of water levels, that contains N total observations. Sites with more frequent flooding receive lower scores and are considered more vulnerable to submergence, whereas sites that are flooded less frequently receive higher scores and are considered less vulnerable to submergence.