Littoral Zone Percent Area

Classify measured lake-bottom patches by a caller colonization depth and sum area; assumes each representative depth describes its patch and does not infer vegetation presence or map geometry.

Description

The littoral zone can be screened as lake-bottom area shallower than a supplied plant-colonization depth.

The littoral zone can be screened as lake-bottom area shallower than a supplied plant-colonization depth. Patch areas permit an area-weighted percentage rather than a count of shallow observations.^[1]

The tool returns littoralAreaM2, totalMappedAreaM2, littoralAreaPercent. The computation uses supplied observations and parameters rather than acquiring measurements.

When to use Littoral Zone Percent Area

Use this for the following task: Classify measured lake-bottom patches by a caller colonization depth and sum area; assumes each representative depth describes its patch and does not infer vegetation presence or map geometry. Prepare observations and calibration parameters on the same unit and reporting basis.

How to use Littoral Zone Percent Area and understand its results

Prepare the measured quantities and supplied model parameters. Match the units and align paired lists before calculating.
Enter patchAreasM2, patchRepresentativeDepthsM, maximumColonizationDepthM according to the field table, then run the tool.
Read littoralAreaM2, totalMappedAreaM2, littoralAreaPercent. Use the calculation below to interpret the selected mean or the model’s signs, units and comparison flags.
Review the supplied assumptions and calibration before comparing or reporting the result.

Input field	Meaning	Value type and bounds	Requirement
patchAreasM2	Patch areas m2	list of number	Required
patchRepresentativeDepthsM	Patch representative depths m	list of number	Required
maximumColonizationDepthM	Maximum colonization depth m	number	Required

Provide aligned positive patch areas and nonnegative representative depths, with a nonnegative maximum colonization depth. Include equality at the threshold.

littoral area=ΣpatchArea for depth≤colonizationDepth; percent=100×littoral/total

The symbols and boundary conditions refer to the supplied fields and the implementation described above.

Output field	Meaning	Value type
littoralAreaM2	Littoral area m2	number
totalMappedAreaM2	Total mapped area m2	number
littoralAreaPercent	Littoral area percent	number

json

{
  "input": {
    "patchAreasM2": [
      100,
      200,
      100
    ],
    "patchRepresentativeDepthsM": [
      1,
      3,
      5
    ],
    "maximumColonizationDepthM": 2
  },
  "output": {
    "littoralAreaM2": 100,
    "totalMappedAreaM2": 400,
    "littoralAreaPercent": 25
  }
}

Limitations and assumptions

Each depth must represent its whole patch. Actual vegetation, light availability and unmapped bottom geometry are not inferred.

Numerical inputs must be finite. Input-shape and calculation checks do not establish measurement quality or the validity of a supplied calibration.

Alternative or Complementary methods

Choose Hypsographic Curve Integration when you need its operation: Integrate observed hypsographic area-depth contours into a cumulative volume curve with trapezoids; contour geometry is supplied and only the measured depth range is represented. Choose Compensation Depth Light Level for the complementary operation: Invert constant optical extinction for a supplied compensation light threshold; a deeper-than-bottom model value is flagged, not silently clipped or declared biologically valid.

Background reference: The Lake and Reservoir Restoration Guidance Manual, second edition.

References

The Lake and Reservoir Restoration Guidance Manual, second edition — U.S. Environmental Protection Agency

Similar or alternative tools

Hypsographic Curve Integration
Integrate observed hypsographic area-depth contours into a cumulative volume curve with trapezoids; contour geometry is supplied and only the measured depth range is represented.
Compensation Depth Light Level
Invert constant optical extinction for a supplied compensation light threshold; a deeper-than-bottom model value is flagged, not silently clipped or declared biologically valid.