A Habitat Suitability Index (HSI) is a paired data set of habitat quality (SuitabilityValue) that ranges from 0 (wholly unsuitable) to 1 (perfectly suitable) and a corresponding habitat variable (HSIValue) such as water depth or velocity. Indices are available for many species and life stages and are commonly used in ecological analyses.
Indices are added to the HabitatSuitabilityIndex table by entering or copy-pasting information into the table (Figure 11). To begin, click the initial row in the table, which is labeled “Click to add new row”. Enter HSI information or copy-paste.
Multiple indices can be stored in the HabitatSuitabilityIndex table – just be sure to use a unique name (HSIName) for each index and take care when entering names. GeoEFM uses the names to identify indices. If the same name is used for two indices, GeoEFM will simply merge their data into a single index, which can lead to odd results. Also, name errors will split a single index into multiple HSIs. For example, an index with 6 rows of information, 4 that use “trout” for the HSIName and 2 that errantly use “trot”, will be treated as two indices regardless of how those data are ordered in HabitatSuitabilityIndex table.
Habitat quality values of a HSI are dimensionless and range from 0 to 1, as described above. However, HSIs relate quality to habitat variables such as depth or velocity, which do have dimensions and units. HSI names can be used to reference that information (e.g., “Little Minnow Spawning – Depth”), which may help avoid errors when applying HSIs.
When done, save edits via the Table - Save feature in Pro. This table “edit and save” functionality is entirely in Pro and does not require the use of any GeoEFM tools. Indices in the HabitatSuitabilityIndex table will be available for application via the Reporting - HSI Calculator tool.
Figure 11. Entering habitat suitability information into the HabitatSuitabilityIndex table. The Little Minnow Spawning – Depth HSI shows that depths become more suitable for little minnow between 0.1 and 1 feet, are ideal between 1 and 3 feet, and become less suitable from 3 to 4 feet, and have no suitability for depths greater than or equal to 4 feet. Note this logic is slightly different than information provided elsewhere in EFM user guidance that says little minnows require shallow depths between 0 and 3 feet for spawning (USACE 2024).