[Talk-is] Adjusting flow of Jökulsá á Fjöllum river

[Sveinn í Felli]

A couple of anecdotes;

The old Danish maps adopted a specific hatch to represent "variable" 
riverbeds, both for glacier floodplains and marshlands.

But the last time a similar situation occurred; a lava flow moving a big 
river representing administrative boundaries; that was in 1783 when the 
second branch of lava from the Laki eruption (Eldhraun) deviated the 
river Hverfisfljót from it's riverbed. In one place the river found new 
course east and south of a mountain called Hnúta [1] instead of running 
north and west of it down into the valley below.

Now, this upper part of Hverfisfljót separated two different types of 
land; the shared common (afréttur) for the county of Kleifahreppur on 
the west bank, and a private property of the farm Dalshöfði in 
Fljótshverfi on the east bank. This distinction used to be hugely 
important because all the farms had duty of supplying n persons (or pay 
else) for collecting sheep in the autumn, hunting foxes, and some more. 
This duty (fjallskil) was considered equal to taxes.

When the farm properties extended all the way up to the glacier, like 
many do in Fljótshverfi, the owner was only responsible to himself and 
his neighbors, but nevertheless had to fulfill the duty of collecting 
sheep, etc. from his land.

With the new course of the river Hverfisfljót, the mountain Hnúta was 
all of a sudden on the west bank inside the shared common area, even if 
still being property of the farm Dalshöfði; so the farmers in Dalshöfði 
became obliged to supply 2 men each autumn to gather sheep from that 
mountain even if they didn't have any sheep on that side of the river.
The interesting or funny part of this story is that this continued to be 
so for about 200 years; it wasn't until in the 1980s when this duty was 
finally abolished for the farmers í Dalshöfði.

But if I'm not mistaken, the administration boundary from pre-1783 still 
persists around Hnúta...

Best regards,
Sveinn í Felli

[1]: <https://www.openstreetmap.org/#map=19/63.97136/-17.94347>


Þann 5.5.2020 20:12, skrifaði Hauke Stieler:
> Hi,
> 
> thanks for the quick reply. As you said, I separated them, so that the
> boundaries haven't moved.
> 
> Hauke
> 
> On 05.05.20 18:55, Jóhannes Birgir Jensson wrote:
>> The boundaries will have to be separated from the river flow.
>>
>> Digital markers are now above geography in boundary marking.
>>
>> -------- Upprunalegt skeyti --------
>> Frá: Hauke Stieler <mail at hauke-stieler.de>
>> Dagsetning: 5.5.2020 16:35 (GMT+00:00)
>> Til: OpenStreetMap in Iceland <talk-is at openstreetmap.org>
>> Efni: [Talk-is] Adjusting flow of Jökulsá á Fjöllum river
>>
>> Hi all,
>>
>> I would like to edit the flow of the Jökulsá á Fjöllum river [0] near
>> the Holuhraun lava field [1] as the lava field is quite new and the
>> river flow outdated.
>>
>> But: The river is also within several administration boundary relations.
>> When I change the river flow, I also change the course of the boundaries.
>>
>> Is that even a problem or is it ok to edit the river and therefore also
>> change the boundaries?
>>
>> In case this is a problem and the boundaries should stay where they are,
>> I would create a new way for the river and tag the existing line with
>> "boundary=administrative".
>>
>> What do you think about this, I would like to hear some feedback :)
>>
>> Hauke
>>
>> [0] https://www.openstreetmap.org/way/741064529
>> [1] https://www.openstreetmap.org/relation/11071456
>>
>>
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>>
> 
> 
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