Łódka · illustrative cross-section

Łódź's rivers under the streets

The Łódka was enclosed in a culvert, but the valley remains. Five points show what can be seen of it from the pavement – and what cannot.

Look from pavements and park paths. Do not enter culverts and do not open manholes.

Qualitative diagram of a cross-section of the Łódka valley Drawing not to scale. The ground descends from the left towards the valley floor; on the slope the three numbered points are Źródłowa, Franciszkańska and Nowomiejska streets. On the valley floor the fourth point is a viewing window in the park above a short stretch of masonry culvert from 1918, and the fifth is the open channel in the park. Between them is a gap denoting an unknown distance.

Qualitative diagram, not a map or a measurement, not to scale.

Highlighted layer: Valley – landform

Qualitative diagram, not a map or a measurement. Vertical and horizontal not to scale; height of the valley floor: not in the source material. The order and heights of points 1–3 are conventional. The ‘?’ in the gap denotes an unknown distance, and the short stretch of culvert does not imply a continuous tunnel. What can be calculated: the section ‘Why the valley is hard to see’.

Layer: valley

1Źródłowa Street

What the source says
The text from ZWiK (Łódź's water and sewerage utility), cited in V2, lists Źródłowa Street among the streets descending towards the Łódka valley. That is all the material says about it.
What the diagram does not prove
There are no elevations or gradient for this street here. The slope in the diagram is an illustration, and its height relative to streets 2 and 3 is conventional.
What to check from the pavement
Which way does the street slope down? Is it the direction in which the ground also falls on neighbouring streets?

Source from V2: ZWiK: W Światowy Dzień Wody zobacz rzekę Łódkę [World Water Day: see the Łódka river] (link kept, not checked in this version).

Layer: valley

2Franciszkańska Street

What the source says
The same information as for Źródłowa: the street is listed as descending towards the Łódka valley.
What the diagram does not prove
There are no data on which stretch descends or how steeply. Numbers 1–3 are not the order on the ground.
What to check from the pavement
Compare the direction of the fall with other streets on this list. A matching direction supports the description of the valley; a differing one needs checking in the source or on an elevation map.

Source from V2: ZWiK: W Światowy Dzień Wody zobacz rzekę Łódkę [World Water Day: see the Łódka river] (to be checked).

Layer: valley

3Nowomiejska Street

What the source says
Listed as descending towards the Łódka valley. V2 showed it together with Park Staromiejski, but the material does not say how far from the culvert it lies.
What the diagram does not prove
A street's slope does not prove that a culvert or watercourse runs beneath it. The valley is wider than the culvert (a general principle from V2, with no measurements in the package).
What to check from the pavement
Walk down the street: does the ground keep falling as far as the park or a distinct valley floor? This page saves nothing.

Source from V2: ZWiK: W Światowy Dzień Wody zobacz rzekę Łódkę [World Water Day: see the Łódka river] (to be checked).

Layer: modern installation

4Park Staromiejski – ‘Oko Śledzia’

What the source says
According to ZWiK, the Łódka flows beneath Park Staromiejski in a masonry culvert from 1918. In the park there is a glass viewing window, ‘Oko Śledzia’, through which the current can be observed.
What the diagram does not prove
The package does not tell us whether the viewing window works today. The stretch of culvert drawn is a shorthand: its length, depth and further course are not given, so its ends are broken.
What to check from the pavement
Look only from the path. Do not go underground and do not open manholes. Check the state of the viewing window in a ZWiK notice or on site.

Sources from V2: ZWiK: Rzeki Łodzi [Łódź's rivers] · ZWiK: Łódka (to be checked).

Layer: former watercourse

5Park Ocalałych – open channel

What the source says
V2 describes the open channel of the Łódka in Park Ocalałych and points to a photograph from 2008 (Arewicz, Wikimedia Commons, CC BY-SA 4.0 according to the description in V2).
What the diagram does not prove
V2 wrote that in the culvert the water flows ‘a few hundred metres further on’. That distance is not in the source package, so the diagram has a gap with no length. The photograph is not embedded here (the page works offline), and its current state is unknown.
What to check from the pavement
Is water visible from the path? If so, it is an open watercourse, not the viewing window. Do not assume it is the same place as point 4.

Links from V2: photo page on Commons · CC BY-SA 4.0 (to be checked).

Three different things in one diagram

  • Valley – landform: streets descend towards the floor. Green.
  • Former watercourse – water visible on the surface. In covered stretches we do not draw its course. Navy blue.
  • Modern installation – masonry culvert from 1918 and viewing window; red marks the change in the river's function. Grey is buildings and structures.

Why the valley is hard to see

A street's gradient is measured in per mille: 20 ‰ means a drop of 2 m per 100 m. The model calculates only this relationship, ΔH = length × gradient, and draws it twice at once – in true proportions and with an exaggerated vertical. It is a teaching model, not the profile of any Łódź street.

Example calculated for 250 m and 20 ‰ (the sliders work when JavaScript is enabled).

Model range: 100–600 m.

Model range: 5–50 ‰. 10 ‰ = 1 m per 100 m.

Vertical exaggeration in figure 2

Drop over the section, ΔH
5.0 m
Slope
20 ‰ = 2.0 % = 1.1°
ΔH in storeys (1 storey = 3 m, assumption)
≈ 1.7 storeys
Angle in figure 2
11.3° (true: 1.1°)

The whole drop over the section is less than the height of one building in the figure (9 m) – which is why the valley is hard to judge by eye.

Assumptions: uniform gradient; no elevations above sea level; a 9 m building (3 storeys of 3 m) is a conventional comparison measure, not the buildings of any particular street.

Figure 1: a street section in true proportions The sloping line of the street is almost horizontal. At both ends stands an identical building 9 m high (assumption), for comparison with the drop over the section.

Thick bar at the bottom = 100 m horizontally (the same horizontal scale as in figure 2). ΔH – the vertical bracket on the right: the drop over the section.

Figure 1 · true proportions (1 : 1). Two identical buildings (9 m, assumption) stand at both ends of the section. The horizontal scale is shared by both figures; the bar is 100 m.

vertical ×10, horizontal ×1

Figure 2: the same section with an exaggerated vertical The same street drawn with the vertical enlarged several times, so it looks clearly steep. The dashed line shows its true slope.

ΔH – the vertical bracket on the right: the same drop over the section as in figure 1, here stretched vertically. The dashed line is the true slope.

Figure 2 · exaggerated vertical (×10). The dashed line is the true slope from figure 1. The same section looks steep only because the figure is stretched.

What this cross-section says and what it does not

It says

That in the ZWiK material cited in V2 the streets Źródłowa, Franciszkańska and Nowomiejska descend towards the Łódka valley, that beneath Park Staromiejski there is a culvert from 1918 with a viewing window, and that in Park Ocalałych the channel is open.

It does not say

No height or gradient of any of these streets, no route of the culvert, no length of the covered stretch, whether the viewing window works, or whether the open and covered stretches lie next to each other. The diagram is not a map.

What we do not draw

A continuous tunnel beneath the whole valley, the sewer network, entrances or manholes. The former river and modern sewerage are not one layer, and the material describes only the river and its 1918 culvert.

What was removed from V2

  • Observation notebook. User entries confirmed nothing, and saving in the browser was not needed. It was replaced by the ‘what to check from the pavement’ questions at each point; the page saves nothing.
  • A/B/C configurations and profile type. They changed only the shape of the drawing, not the number. Two parameters and the formula ΔH = length × gradient remain; the ‘subtle / clear / steep’ thresholds were removed as arbitrary.
  • River choice and ‘underground layer’ toggle. They were replaced by a single cross-section with three distinguished layers; Lamus and Jasień appear lower down as short pointers.
  • Embedded photo from Commons. An external image broke the offline principle. A link remains at point 5.
  • Card-printing button and three ‘recognition rules’ cards. The content of the rules was moved to the point cards (‘what to check from the pavement’) and to the ‘Further’ section, so separate cards and a button to print them became redundant.

Further: other rivers, separate essays

Lamus

According to ZWiK, a tributary of the Jasień, flowing beneath the grounds of the former Grohman works to Park Kilińskiego. V2 points there to the ‘Szybki Lamus’ observation point, with a crank that lights up the current. Whether it works today needs checking.

Jasień

The river of textile Łódź, largely culverted, but from Piękna Street to its mouth flowing in an open channel, according to V2. The open stretch by Piękna Street concerns the Jasień, not the Łódka.

Ponds

The ponds in the parks, among them Park Reymonta, Park Widzewski and Park Nad Jasieniem, V2 describes as former industrial impoundments for weaving and spinning mills. Details to be checked in the sources below.

Sources

Links carried over from V2. In this version they were not opened or verified again; they are clickable links, not dependencies of the page. The content of each needs checking before publication.

The drawings on this page are V3's own schematics (Sonnet model), with no third-party rights; they are not a map, a measurement or a reconstruction. System fonts. There is no saving of data in the browser, no cookies and no external resources here.