Method
How the waterfall rule works, and how well it works
Some places are real and unrecorded. A waterfall can exist on the ground, be visible in the published contours, and appear in no gazetteer and no feature layer at all. This rule finds those, and this page publishes how often it is wrong.
On-ground signage and temporary closures override this page. Always.
The rule falls-rule/1
The rule reads published elevation contours along mapped watercourses and looks for a drop of at least 12.0 m over a run of no more than 40.0 m. Where the terrain falls that fast over that short a distance, the rule proposes a waterfall candidate.
That is all it does. It is a statutory-free, purely topographic inference over an official layer, so a candidate it finds is published at C — provenance grade C: Statutory inference — never higher. It cannot see water, flow, season, or whether anything is there at all in a dry year.
A rule identifier is versioned on purpose. If the rule changes, published candidates change with it, and the identifier on each place page says which version found it.
How well it scores Against places the state does map
The rule is scored against waterfalls the state already maps: a candidate that matches a mapped waterfall counts as a hit, one that does not counts as a miss, and a mapped waterfall the rule fails to propose counts against recall. At the chosen parameters it scores 0% precision and 65% recall, for an F1 of 0.01.
Read that plainly: roughly 100% of the candidates this rule proposes do not correspond to a waterfall the state maps, and it misses roughly 35% of the ones it does. Both numbers are the reason a rule-found place is graded C and labelled as a rule output on its own page.
Precision is scored against the state's own map, which is itself incomplete — a candidate counted as a false positive may be a real, unmapped fall. The score is honest about the comparison, not a claim that the state layer is the truth.
Every parameter pair tried Not only the winner
| Minimum drop | Maximum run | Precision | Recall | F1 | Chosen |
|---|---|---|---|---|---|
| 5.0 m | 40.0 m | 0% | 93% | 0.00 | |
| 5.0 m | 60.0 m | 0% | 98% | 0.00 | |
| 5.0 m | 80.0 m | 0% | 98% | 0.00 | |
| 8.0 m | 40.0 m | 0% | 82% | 0.00 | |
| 8.0 m | 60.0 m | 0% | 87% | 0.00 | |
| 8.0 m | 80.0 m | 0% | 93% | 0.00 | |
| 12.0 m | 40.0 m | 0% | 65% | 0.01 | chosen |
| 12.0 m | 60.0 m | 0% | 75% | 0.00 | |
| 12.0 m | 80.0 m | 0% | 78% | 0.00 |
A rule that is only shown at its best setting is a rule nobody can check. The whole grid is published so the trade-off between finding more places and being wrong more often is visible.
What this page will never do
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No user pins
Every fact here traces to a government layer or a statute and carries a grade, A to C. Community names are quarantined at grade D and labelled as such. Nothing on this page was dropped on a map by a stranger.
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No invented lawfulness
Where tenure cannot be confirmed from the public record, the page says so instead of endorsing the route or quietly hiding it. Where no lawful corridor exists at all, none is published — the refusal is the answer.
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No safety pretence
A tier is a tenure verdict, not a difficulty or safety rating. Unmanaged terrain, cliffs and flash flooding are not in the cadastre. The engine reads land records, not the weather.