Cross-section through a single furrow in loess, at human scale. The same shape can be left by a road, by water, or by both. The shape alone does not settle this.
Features observed in this diagram
Documenting a former road
All four cuttings are drawn at the same scale, so a metre is the same length everywhere. Move the cut along the axis of the stretch and watch when similar furrows stop being similar. The dimensions are the author's model assumptions, not measurements of any terrain.
Without JavaScript the middle of the stretch is shown (cut at 50%). Moving the cut requires a script.
Longitudinal section, not to scale: the floor descends towards the middle of the stretch. This is a model assumption (a sine curve), not a measurement of any terrain.
Deepest at this cut: D (h = 3.8 m).
Floor not narrower than the 1.5 m reference segment: A, B, C. Narrower floor: D.
Most similar floor proportions b/h: A (0.81) and B (0.91). A similar ratio does not mean the same form: compare the slopes.
At this cut all the cuttings are at least 1.0 m deep and their slopes at least 25°.
How to read the drawings. Ochre is loess, white is the space of the cutting. The thin vertical line on the left is the depth h measured from the upper edge (in B from the edge of the higher side). The thin line below the floor is the floor width b. The thick blue line is the conventional 1.5 m reference segment, an auxiliary convention and not the dimension of a vehicle. The bar in the bottom left corner is 1 m long. The figure is 1.75 m tall. B has two angles: upper / lower slope. In cross-section C looks like one wide channel, but in plan it could be several parallel furrows, which the cross-section does not show.
Enter dimensions from your own tape measure, plan or assumption and see the profile to scale with a human figure and the 1.5 m reference segment. The calculator works out a symmetrical trapezium. It is the geometry of the numbers you enter, not an assessment of how the form originated.
Without JavaScript the result is shown for the default values b = 2.5 m, h = 3.0 m, B = 7.0 m. Changing the dimensions requires a script.
Model: symmetrical trapezium. The result describes the geometry of the numbers entered; it does not settle what the form is.
Lines as above: the thin one below the floor is b, the blue one is 1.5 m, the bar in the corner is 1 m. The scale of the drawing is fixed (the frame is 14 m wide), so a small cutting stays small.
A cross-section tells how a cutting in loess looks today. It does not tell who hollowed it out, when, or what travelled along it.
The same loop can also work where there was never any road. That is why the erosional gully (D) is the misleading form in this set. How many years this takes depends on the place. The page gives no such figure.
Possible readings. A channel shaped by traffic and water runoff. This is a hypothesis to be tested, not a result.
To check. Georeferencing of old maps, layers in the floor (whether there is a hardened surface beneath the silt), a search of written sources.
Possible readings. A road laid across the hillside. A ditch or undercutting by water gives a similar cross-section too.
To check. Course relative to the contour lines in the terrain model, continuity beyond the studied stretch, old maps.
Possible readings. Several parallel lanes used in turn, or one wide excavation. V2 described this as avoiding worn-out ruts, but without a source reference, so treat it as a hypothesis.
To check. A plan view from above, not a cross-section: whether the furrows are parallel and whether they join. Written sources.
Possible readings. A cutting made by water with no road, or a former road cut through later by water.
To check. The catchment in the terrain model, sediments in the floor, traces of use beneath the debris, old maps.
The links were carried over from version V2 and were not opened when V3 was built. The match between the descriptions and the sources needs checking before they are treated as confirmed.
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