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    Canonfire :: View topic - Nyr Dyv surface level?
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    Nyr Dyv surface level?
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    Journeyman Greytalker

    Joined: Aug 22, 2005
    Posts: 298
    From: Ahlissa

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    Wed Dec 02, 2015 8:07 pm  
    Nyr Dyv surface level?

    I need some input from all you Greyhawk experts!
    One of my example map I want to create soon are Walworth Isle, the island in Nyr Dyv where Admundfort are located. Its small size and the fact that it's an island and not to detailed to begin with makes it a good candidate for me to start with.
    I've already made about 6 versions of it as I've worked on the technical bits. But now I've so close to getting all the things I want to work actually working, so this time it it hopefully for real.
    One of the things I'm now able to do is to map lakes and rivers properly which means rivers flow downstream (I can acctually make them flow upwards too if needed Wink ) and lakes surfaces can be where needed.
    So my question is what are the surface level of Nyr Dyv, and also the other big lakes?
    My idea have been that Nyr Dyv are close to sea level. Selintan and Nesser rivers seem to be flowing gently and I think I've read of extensive river traffic along both of them.
    Black Hand of Oblivion

    Joined: Feb 16, 2003
    Posts: 3835
    From: So. Cal

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    Thu Dec 03, 2015 2:16 am  

    Right. Rivers that flow gently, and which are therefore very easily navigable upstream (which the rivers the central Flanaess are), are very close to sea level. The lower Mississippi River for instance is very much that way, with its most notable increases in elevation occurring in Illinois and farther north. 27 locks and/or dams are required for vessels to navigate the northern 2,000 km of the Mississippi River, while none are required for the 1,600 km (about 1,000 miles) long lower portion of the river (Google! Happy).

    As the central rivers of the Flanaess are navigable from Wooly Bay all the way to the Nyr Dyv, and even to Lake Quag (which is somewhat remarkable considering the rugged terrain the Velverdyva River cuts through as it nears Lake Quag), the water level of would probably be less than 300 feet at the highest point along the route (i.e. Lake Quag), but it could be much less than that even. Elevation would of course drop all the way to 0 feet as the Selintan River empties into Wooly Bay.

    You can Google The National Weather Service reports to see information on the water levels of the lower Mississippi River at various times of the year, and Google various locations along its route. Also, look up lakes at various places along the route of the Mississippi River, and you will get an idea of what the the local land, river, and lake elevations in those areas are too. Put that all together and you should have a solid foundation on which to base the water levels of the Nyr Dyv, Lake Quag, other bodies of water, and of the rivers at various locations along their routes.
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    Last edited by Cebrion on Fri Dec 04, 2015 1:57 am; edited 1 time in total
    Journeyman Greytalker

    Joined: Mar 12, 2008
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    Thu Dec 03, 2015 1:40 pm  

    Lake Quag would be a bit higher than 30 feet above sea level, I expect. St. Louis is about 800 feet above sea level, after all.

    One foot drop per mile of river would still put the Nyr Dyv about 100 feet above sea level (about what I'd expect, given the need to cut through the Cairn Hills), and another 200 feet up to Lake Quag

    Assuming I remember the distances correctly, anyway.
    Grandmaster Greytalker

    Joined: Nov 07, 2004
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    From: Mt. Smolderac

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    Thu Dec 03, 2015 2:56 pm  

    Cairo is 315' above sea level and at about the 1000 mile mark along the Mississippi. I think I calculated the Nye Dyv to be about 250 or so miles up from the Selintan's mouth although that was based on the hex map so let's just say 300 with all the twists and turns. Natchez is 300 and some change up the Mississippi and has and elevation of 217'.
    Black Hand of Oblivion

    Joined: Feb 16, 2003
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    From: So. Cal

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    Fri Dec 04, 2015 1:56 am  

    OOPS! I left a zero off of there. Laughing Yes, 300 or so. Plenty of distance to drop down to zero. A 300 foot drop along a 52 hex distance, at 30 miles per hex (8,236,800 feet), would make for an average incline of about 3/10ths of a degree. A 30 foot drop over that distance would make for an average incline of about 3/100ths of a degree, meaning the water would be moving at a literal crawl. I think it is mentioned that there is a noticeable current to the rivers in most places (especially where they bottleneck a bit), though I'll leave it to you lot to hunt down any extant info on the speeds of the rivers. Razz

    Okay, I got lucky and found this when I Googgled "river incline and current speed":

    https://books.google.com/books?id=E2iQGWzudxsC&pg=PA149&lpg=PA149&dq=river+incline+and+current+speed&source=bl&ots=ukkNSs_GLN&sig=EwAp8dQu36Lfp7_qn6jwGYQsnkk&hl=en&sa=X&ved=0ahUKEwjHrfzL_8HJAhUBQCYKHY7ZA6oQ6AEIHDAA#v=onepage&q=river%20incline%20and%20current%20speed&f=false

    See section 3.1 on page 149 and thereafter for information on current speeds likely conditions of navigable rivers, their banks, their depths, and the land round about. More information on this can no doubt be found, but I leave it to you to decide how much is enough before you get on with the fun stuff.
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    Paladin

    Joined: Sep 07, 2011
    Posts: 833
    From: Houston Texas

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    Thu Feb 04, 2016 2:06 pm  

    Vulcan wrote:
    Lake Quag would be a bit higher than 30 feet above sea level, I expect. St. Louis is about 800 feet above sea level, after all.
    ..........

    Actually the St Louis / Hannibal Area is less than half that elevation.

    As Big C points out (and having worked with the Corps of Engineers on various projects on the Mississippi pretty much from end to end in my career) the upper Mississippi consists of ALOT of locks, Weirs, and Dams to better control the flow rate of water than from the times of Mark Twain (a former Hannibal Resident by the way). While the lower portion slows due to natural contours of the continent and the aid of other tributaries as well as the Atchafalaya Swamp basin. Below are some links for the curious and Anna, the national map.gov site used to have vectored and raster type files that may also prove useful to use as well...

    just my 2cp
    DLG
    For What its worth Wiki Says wrote:
    The source of the Upper Mississippi branch is traditionally accepted as Lake Itasca, 1,475 feet (450 m) above sea level
    From St. Louis to the Ohio River confluence, the Middle Mississippi falls 220 feet (67 m) over 180 miles (290 km) for an average rate of 1.2 feet per mile (23 cm/km). At its confluence with the Ohio River, the Middle Mississippi is 315 feet (96 m) above sea level.
    The Mississippi River empties into the Gulf of Mexico about 100 miles (160 km) downstream from New Orleans. Measurements of the length of the Mississippi from Lake Itasca to the Gulf of Mexico vary somewhat, but the United States Geological Survey's number is 2,320 miles (3,730 km). The retention time from Lake Itasca to the Gulf is typically about 90 days.

    Note, this is only partly true since the corps of engineers have been diverting roughly 25% of the Mississippi into the Atchafalaya river and swamp well east of Baton Rouge and New Orleans for some time now.. but hey that helps the crawfish season Laughing

    http://cgee.hamline.edu/rivers/Inquiry/CF/cf_1.htm
    http://nationalmap.gov/
    http://viewer.nationalmap.gov/viewer/nhd.html?p=nhd
    Apprentice Greytalker

    Joined: Aug 03, 2002
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    Thu Feb 04, 2016 11:58 pm  

    Anna, if you want to displace the US point of view to Europe you may find some inspiring material in the most beautiful and famous lakes in Europe:
    Saimaa Lake , 249 ft
    Constance Lake, 1296 ft
    Orhid Lake 2273 ft
    Loch Awe, 118ft
    Orta Lake, 950 ft
    Geneva Lake, 1220 ft
    It sems the majority of European lakes are between 330 and 850 ft in elevation.
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