Description
Compute secondDistance-firstDistance, reverse sign when inlandPositive is false, and divide retreat by elapsedYears.
Landform change is often summarized by differences in height, area, volume, or storage over a defined interval. A signed budget preserves gains and losses, but its meaning depends on a common spatial support and reference surface.
Compute secondDistance-firstDistance, reverse sign when inlandPositive is false, and divide retreat by elapsedYears.
When to use this tool
Use Shoreline Retreat Transect Two Date Term when you need a local geomorphic change or storage-budget calculation.
How to use the tool and how it works
- Enter firstDistance, secondDistance, elapsedYears, inlandPositive. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read retreat, retreatPerYear. Use the output convention below.
Require positive elapsedYears. Compute secondDistance-firstDistance, reverse sign when inlandPositive is false, and divide retreat by elapsedYears.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| firstDistance | First Distance | Required. Finite number. |
| secondDistance | Second Distance | Required. Finite number. |
| elapsedYears | Elapsed Years | Required. Finite number; strictly above 0. |
| inlandPositive | Inland Positive | Required. Boolean. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| retreat | Retreat | Required. Finite number. |
| retreatPerYear | Retreat Per Year | Required. Finite number. |
{
"input": {
"firstDistance": 20,
"secondDistance": 35,
"elapsedYears": 5,
"inlandPositive": true
},
"output": {
"retreat": 15,
"retreatPerYear": 3
}
}Limitations and assumptions
- Distances share a common transect origin, unit, and orientation; positive retreat follows the supplied inland convention and no shoreline extraction, trend uncertainty, or future hazard is inferred.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Compare aligned surveys and their uncertainty over the same spatial support. A full mass or volume balance should include omitted fluxes, evolving geometry, and measurement error.
References
Similar or alternative tools
- Bank Retreat Reference Axis Sign
Multiply laterPosition-earlierPosition by that sign and divide for annualRate.
- Erosion Pin Reference Exposure Delta
Return second-first, subtract signed pinMovement for correctedErosion, and divide by years.