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The great plains are well-known for their flatness but they rise from about 200m at st Louis on the Mississippi river to almost 2000m at the "mile high city" of Denver next to the rocky mountains. If I was placed randomly somewhere on this slope (such as in the middle of Kansas), would I be able to infer which way was uphill without relying on the knowledge that it rises to the West?

The slope itself is about a 0.1-0.2% grade, which (I think) is not enough to sense on foot (with a streamlined fairing bicycle it may be). However, there are features such as small hills and cliffs that are eroded by water. Do these features tend to be "pointed" in the downhill direction? For example, is the top of a Buffalo Jump usually uphill? Could I follow a small stream up-current and then try to keep following the ridgeline upwards when I reach the source of the stream?

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  • When driving on flat road, look at the instaneous mileage., it drops when the engine is working to go uphill ( on cruise control). I noticed this in west NE, east WY , and east CO. Looking out the window, I was sure the ground was level but the MPG showed the rise. Aug 1 at 15:30
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    @blacksmith37 What about wind? Prevailing wind tends to also blow west to east, and air drag is HUGE at highway speeds. Aug 2 at 1:31
  • The wind is a relative constant . After a thousand miles one has a good idea of the level road instantaneous mpg. Then ,when going up a grade the change in mpg is caused by the grade. If a sudden storm front hits, that makes a difference. Aug 2 at 20:22
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While you are unlikely to be able to identify the uphill trend of such a large area, water is the key to doing so if limited to natural features. It would be difficult to follow water to the absolute highest point in an entire region, but you will at least get to local high points.

As you noted the general slope is very shallow. Local peaks will distort the terrain much more than the region-wide trend in elevation. As other comments and answers suggest, upstream will always lead you to higher elevation. That and other regional trends such as prevailing winds/weather could offer clues. However, these features are also susceptible to local trends misleading you from the regional trend. The key to streamflow is that even the local maxima (headwater of a smaller watershed) area nested within the larger Mississippi River Basin.

As an example of this, consider a quick USGS StreamStats analysis (screenshot below): USGS StreamStats analysis showing watershed from USGS gauge near Manhattan, KS and downslope flow path from Denver, CO

In this image the yellow area is the drainage basin flowing into the USGS stream gauge (06887005) near Manhattan, Kansas, and the red line is showing the downslope flow path of a raindrop falling in Denver, Colorado. If you found a stream of any size in this area northwest of Manhattan, Kansas, and you followed it upstream, you would go in the widening, northwest direction of the yellow drainage basin. Importantly, you will reach a local maxima which stops much sooner than Denver.

From that local maxima you can potentially get a view of the surrounding area, and you can try to identify a higher-order stream (meaning a larger stream that has more upland streams converging to contribute to this one). As you follow that one, you will be following a general upward trend.

Here is another screenshot of the boundary between that Manhattan, KS, watershed alongside the flowpath from Denver, CO. screenshot of the boundary between that Manhattan, KS, watershed alongside the flowpath from Denver, CO.

Looking at a terrain map of that area between the local drainage basin and the flowpath to Denver, you can see it is quite flat but it would still bring you next to the higher-order Platte River which you can follow upstream.

Terrain map showing how one smaller watershed leads to the larger Platte River basin

If you followed the Platte River upstream, you will spread in one direction of its headwaters, getting an imprecise but general trend upward. If you kept doing this, you would reach a local maxima of the regional basin (e.g. any peaks in SE Wyoming), if not the global maxima (Fishers Peak, CO) of the basin.

Platte river basin map

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(Un)Follow the water. Water will always flow down-hill. If you go in the opposite direction to the current, you will be travelling uphill.

If you were randomly placed and have a map showing waterways, but not the contour lines (e.g. google maps street-map style presentation) you can get a generalized idea from the river direction(s). If you were traversing on foot, with such a map you could cut out some of the loops/meanders that rivers take on "flat" terrains such as plains.

This is also survival advice doing the opposite - if you ever get lost with no hope of recovery (e.g. no-one knows where you are or no-one will be looking for a week or two), then follow the water down-hill. You will eventually meet a larger waterway and human residences and towns/cities are almost always placed near a source of water.

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  • +1 but in some places, you will arrive at an impassable cliff and a waterfall.
    – ab2
    Aug 1 at 16:48
  • @ab2 - you don't have to walk right beside the water, just follow in the general direction. If you have a cliff and waterfall - find a way around them and re-join the water later.
    – bob1
    Aug 1 at 20:37
  • Following the water downhill won't work here. Of course this isn't on the Great Plains. Theoretically, you could bypass the falls, but only if walked upstream first.
    – ab2
    Aug 1 at 22:18
  • @ab2 - I disagree, all you have to do is follow the direction of the water, not the water itself, so you could head west along the canyon wall and head down a Snow-Creek Trail, or head East and come down Tenaya Creek itself.
    – bob1
    Aug 2 at 0:26
  • Downhill water is a good survival tip for most areas and would eventually get you to the Mississippi. However, uphill could lead you to a local high in the terrain (i.e. a really subtle peak). So would this actually work well? Aug 2 at 1:30

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