Author Topic: Navigability of streams at map generation  (Read 635 times)

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Offline AP

Navigability of streams at map generation
« on: July 19, 2017, 02:06:43 PM »
Is there any way to define /improve the extent to which rivers and streams, auto generated by the map creator, are navigable?

It seems that by default, around 75% of them are entirely non-navigable. Which is a bit frustrating when trying to make use of them for transport. I appreciate the upper reaches of a stream should be shallow, but the game mechanics only seems to make them get deeper, where two streams merge together, which doesn't happen all that often.

Therefore I suggest something needs tweaking so they are at least navigable by the smallest of craft for the majority of their existence, even if "big rivers" are a bit rarer.

It might also be good if,for instance, one could "dredge" a river to make it deeper, upgrading it to the next format up. At present, one can only upgrade it to a canal, which comes with considerable ongoing expense.
« Last Edit: July 22, 2017, 02:49:22 PM by AP »

Offline jamespetts

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Re: Navigability of streams at map generation
« Reply #1 on: July 22, 2017, 10:23:21 PM »
Thank you for your feedback. The system for generating rivers is unchanged from Standard. May I ask what the size of your map is and how many rivers that you are generating? Having more rivers per unit of size will greatly increase the chances of any given river being navigable due to the merging mechanic (which is realistic in any event).

I do not think it unrealistic that a large proportion of rivers are unnavigable; most rivers in reality are unnavigable, but they are so small that one does not usually notice them: in towns, they are put into culverts, and in the countryside, they can only be seen close up, and are crossed by small bridges.

As to dredging rivers, any dredging would of course have to be done regularly, so would have the same economic effect as canalising a river, requiring an ongoing maintenance cost that consists mostly of dredging in any event.
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Offline AP

Re: Navigability of streams at map generation
« Reply #2 on: July 23, 2017, 08:14:06 AM »
The settings I use vary with the map. I usually try to have more rather than less,but after recently learning they are heavy on computational power to create, may revise that. Usually I've aimed for say 100 rivers in a 1000x1000 map.

I'm not disputing the realism of unnavigable rivers, I'm saying it's pointless to simulate them. They are just eye candy at that point.

I think you may be mistaken about rivers only getting bigger as streams merge? I'm not a hydraulic expert but my understanding was water percolates from rocks and geology into watercourses along their entire length.


Offline jamespetts

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Re: Navigability of streams at map generation
« Reply #3 on: July 23, 2017, 11:42:37 AM »
I suspect that your number of rivers is considerably too low - I suggest multiplying the number by about four or five to get a more realistic number of rivers. It might increase map generation time - but it might well be that you will want to set aside some time for map generation in order to allow for this so that you get a better number of rivers and therefore more navigable rivers.

However, non-navigable rivers are not just for decoration: they are a geographic feature that must be crossed at some expense; they carve little valleys out of the landscape that need engineering to deal with; and, during the map generation phase, they attract towns to be built upon their banks. They can be upgraded to canals at lesser expense than building a new canal from scratch.

As to percolating groundwater, I do not think that there are any rivers that reach a navigable depth just by these means, are there? This would only occur near a river's source, resulting in a larger stream, not a navigable river. The groundwater would not know which bit of land that has a river running on it to percolate specifically to there and nowhere else around, so this can only happen in a place where groundwater percolates to the surface in any event (i.e., not most places in downstream rivers).
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Offline AP

Re: Navigability of streams at map generation
« Reply #4 on: July 23, 2017, 11:50:11 AM »
Quote from: jamespetts

As to percolating groundwater, I do not think that there are any rivers that reach a navigable depth just by these means, are there? This would only occur near a river's source, resulting in a larger stream, not a navigable river. .

Where do you think rainwater goes where it falls on a  dry flood plain?  A river is just where the water table moves from below ground to above ground.  it drains the water table wherever it occurs. That is why when they drained the fens or Somerset levels,  they did so by digging new rivers. I suspect most such rivers are navigable by shallow craft or kayaks.
« Last Edit: July 23, 2017, 01:02:02 PM by AP »

Offline jamespetts

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Re: Navigability of streams at map generation
« Reply #5 on: July 23, 2017, 12:01:17 PM »
Where do you think rainwater goes where it falls on a  dry flood plain?  A river is just where the water table moves from below ground to above ground.  it drains the water table wherever it occurs. That is why when they drained the fens or Somerset levels,  they did so by digging new rivers.

Actually simulating that would be an enormous task; but do you know of any places where rivers actually become navigable without being joined by any other rivers/streams at all?
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Offline AP

Re: Navigability of streams at map generation
« Reply #6 on: July 23, 2017, 01:06:34 PM »
Every river in the country.

If you are suggesting rivers only get their water from Springs,high in the hills at the end of each tributary,  then by definition those Springs are higher than most of the rainfall catchment area within the watershed.

Therefore you would be proposing all of the rainfall falling within the watershed on land of lower altitude than the springs, which is most of it, does not enter the rivers, by your model.

I suggest it does, all the way along the river's length.

The joining together of rivers isn't the only factor of relevance. It is more relevant in terms of network design,  than in terms of depth, unless perhaps you were to simulate every drainage ditch, rine and culvert...

Which is why rather than having an even more complex simulation,  I suggest just making long rivers naturally get deeper as a function of length alone.

Offline jamespetts

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Re: Navigability of streams at map generation
« Reply #7 on: July 23, 2017, 01:16:18 PM »
As noted earlier, the river generation is inherited unchanged from Standard. This would require some significant amount of time in researching rivers (can you find an example of a navigable river with no tributaries?) as well as implementing the proposed feature, based on that research. At present, my work needs to focus on balancing related matters and fixing bugs. An overhaul of terrain and river generation may well be worthwhile one day, but, in the meantime, I do suggest that you increase the number of rivers generated in order to get more navigable rivers.
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Offline AP

Re: Navigability of streams at map generation
« Reply #8 on: July 23, 2017, 02:38:17 PM »
This would require some significant amount of time in researching rivers (can you find an example of a navigable river with no tributaries?

Searching for a navigable river with no tributaries isn't relevant.

There are unlikely to be many, because rivers usually have many tributaries but many of them are very minor indeed. It also depends on definition of navigability and with many rivers having been improved over the centuries, gets rather complex.

But it's irrelevant, because simutrans rivers are highly unlikely to have tributaries, under the current code, (in that way differing from their natural counterparts quite significantly).

Therefore the relevant comparison, is % of river length that is navigable, in both cases.

If we are seeing rivers more as "landscape obstacle" than "transport feature", that goes someway to explaining their relative lack of utility.

Offline jamespetts

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Re: Navigability of streams at map generation
« Reply #9 on: July 23, 2017, 02:42:14 PM »
I do not find that rivers are unlikely to have tributaries - but I use much higher numbers for river generation than do you. I think that the river generation system was calibrated with a higher number of rivers per area of land in mind than that at which you use it.
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Offline scamps

Re: Navigability of streams at map generation
« Reply #10 on: July 30, 2017, 05:47:51 PM »
Another reason to review river generation sometime is meters-per-tile setting. In real life riers wider then 125m are not too rare. They are navigable by river/sea class ships.It would be fun to have several tiles wide rivers in Simutrans.
Only restriction that comes to mind: changing height of such river is not supproted.

Offline jamespetts

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Re: Navigability of streams at map generation
« Reply #11 on: July 30, 2017, 08:29:24 PM »
Another reason to review river generation sometime is meters-per-tile setting. In real life riers wider then 125m are not too rare. They are navigable by river/sea class ships.It would be fun to have several tiles wide rivers in Simutrans.
Only restriction that comes to mind: changing height of such river is not supproted.

Extra wide rivers (consisting, not of river tiles, but of "water" tiles as used in lakes or the sea) would definitely be a worthwhile feature, but it would also require some quite radical changes to the code that would take a very large amount of coding work, so, without significant numbers of additional programmers, this is not likely to be possible in the short-term, as the current focus is balance.
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