A "ridge line" as a natural boundary?

[Lee Hixson]

Been surveying since 1965 and never run into this kind of description. It's for a county line. The legal description states "thence west, on said township line to the ridge dividing the waters flowing into ____ Creek and ___ Creek, from those flowing west into the north fork of ____ Creek and ___ Lake; thence northerly, along said ridge to the summit line of the Coast Range...."

That's it. So the county line runs along a ridge line and no one has ever surveyed it before, not once, not even back when the county line was created. Examining the USGS quad sheet, there are portions where it's very obvious where the ridge line is, but then it drops down the hill and hops across a small valley to the top of another hill and the beginning of another, much less well defined, "ridge line" and so on.

Mulling this over, I figure that one way to tackle this would be to fly it--map the whole ridge line with 1-foot contours which should allow you to go into the drawing and draw a line (a break line, in effect) that would follow the high points all along the ridge.

Walking it with a rover would not only be tedious (it's a 10-mile long stretch) but there would no doubt be flatter areas where it would be hard to visually decipher the high line. Having good contours would seem to be the way to go.

For the time being I think it's best to not get into the particulars of the area and the purpose of the survey. Suffice it to say that the county line has to be located. Oh, and the description for the neighboring county? They do a cop out and merely call to the west line of the first county.

Anyone ever run into a description like this? Thoughts?

[pls7809]

Interesting. How long of a line is this ridge line? That could be an expensive aerial.

[Lee Hixson]

It's a 10-mile long stretch. I've already talked to one of the county surveyor's and he was on board with the aerial approach, but it's early on and I'm thinking that if this project actually got the green light it could quickly become a magnet for all sorts of input...engineers, surveyors, county supervisors, property owners nearby...people coming out of the woodwork with their two cents. And with that much input, on such a shaky description, could be a rough ride!

[Lee Hixson]

Apparently not, as the county surveyor just chuckled a bit when I said, "So really? There's no other description?" and then told me that, "No, the ridge line is it and no one's ever surveyed it."

[E_Page]

This sounds like a really interesting project, Lee.

Many of the County descriptions are just like that, with the neighboring county simply calling to the boundary of the other. Drainage divisions (Ridge lines) and waterways are used in many portions of the boundaries of many of our counties.

Such descriptions are not very common among private boundaries here, but are quite common in the colonial states. Sometimes they are not even as descriptive and definite as what you've stated.

If you think about it, the location described is very specific and leaves no ambiguity. Water hitting the ground in that area, barring the effects of ground infiltration, will either flow into one drainage or the other, depending entirely upon where it hits the ground. Along some rather finite line, there will be a location that divides the drainages, where water at one spot flow one direction, and if it were to land just a few inches away, it would flow in the opposite direction. It may not be well determined in terms of known location at this time, and in many locations it may not be easy to determine, but it is a very definite location and I think you are on the right track to find it.

It's actually more definite and more retraceable than are boundaries defined at their endpoints by artificial monuments which had been set and have since been lost.

Buy in by both County Surveyors as to methodology prior to determination would be a very good thing.

[D Ryan]

Lee-

That's pretty typical for County line descriptons I've seen up north. Usually the top of a major ridge is not a line that would need to be laid out. Why does it need to be located?

Dave Ryan
Humboldt County

[LS_8750]

Sounds like fun. Are we to consider groundwater flow direction? I think the Louisiana Purchase had some description similar to this with respect to the Mississippi watershed.

[Lee Hixson]

After thinking about it some more, and doing more research, I now understand two important, unfortunate aspects about drainage ridge lines:

1. Ridge lines are not immutable. While not as bad as the movements of rivers and streams, nonetheless they are, in fact, subject to erosion and tectonic shifts. Not really a smart thing to "call to" one of them for a legal boundary.

2. Where exactly is that ridge line? They used to be located by manual interpolation of contour lines. GIS software can now automatically extract ridge lines from topographic data, making it easier, and far more accurate to locate them, especially in areas of "rounded topology." The accuracy of the extracted line is directed related to the quality of the topographic input: not so accurate with contours from a Quad map, but very good if based on a good aerial.

Conclusion: a modern aerial--processed by GIS software--would probably be a satisfactory methodology to use to locate the county line. Some well defined caveats would be called for, 1) making explicit exactly how the line was arrived at, and 2) pointing out that it is only accurate "at this point in time" and could shift over time.

[E_Page]

The change in the location of ridge lines would be so minimal, so imperceptible so as to be negligible in a year to year, decade to decade, and unless in a geographically active area, century to century comparison.

I would think that the ground one might set an artificial monument into would be considered to be every bit as immutable as the artificial monument depending upon that ground for stability.

[LS_8750]

Ha! Set 600 ton boulder, tagged LSXXXX.

[goodgps]

I agree with the "Floating ridgline" theory. Also Like the aerial flight method, with some very nice mental gymnastics involved. Accuracies etc.
It may also be considered to pick a method of your choice and budget, then compare the resultant land area with that of the assessed value, just in the interest of fairness.
I have experienced the same as Evan has stated (roughly) . . . that the ridge is NOT exactly the center of the hill, but rather an imaginary rainfall line, or, in general, a line that could be followed on foot etc. .
Question ? Are you goint to Monument the entire line ??? Sorry I may have missed that above :-(

[JoeC]

Sounds like you might your hands full on this.
My questions are –

Do the lines of occupation come into play and is a boundary line agreement applicable here?

Does the Board of Supervisor of each county have to agree to the line shown on the ROS?

What would happen to properties presumably to be one county and your survey now shows them in the other county?

I'm asking because I don't know..

Also, I would want to know more the County Surveyors chuckle.

Good luck.

[Lee Hixson]

I would be reluctant to set any monuments. The GIS-produced ridge line would be a line only in the lay sense of the word, same as if you were to draw a freehand line on a piece of paper. Nowhere would you have a line segment of any measurable length--just a collection of points. It would be constantly varying in direction. I suppose you could pick "a" point and set a monument. But even that would be risky because the location of any given point would vary depending on the method used to define the ridge line.

Go back 50 years. If a surveyor did a manual interpolation, creating a ridge line, and set a monument at some point along that line, would it match a ridge line produced by aerial photography and GIS software? No. How about contour data produced by airborne lidar. Or if the same data were processed with different software? No thanks.

And Evan, I agree with you that in the vast majority of cases any changes would be minimal and/or non-frequent. But I ran across a university study where they used DEMs to model different watersheds (and their ridge line boundaries). They wanted to know what would happen if a local perturbation occurred near a ridge line as with a landslide (big or small), a sink hole, or an earthquake.

At a location near the Canadian border a 2-meter change caused a change in the location of the ridge line, causing a shift of 3,730 sq km! Admittedly, this was in a relatively flat area, but it can happen. And, as commonplace as landslides and tectonic movements are in California, this isn't out of the question.

At the end of the study their summary stated: "...we were able to show that small and localized perturbations can have a large impact on the shape of watersheds even at very long distances, hence having a non-local effect."

[Lee Hixson]

Steve...

I haven't pulled many deeds yet. Most parcels are sectionalized. However, along the county line there was one parcel that was rectangular on 3 sides (aliquot lines, I'm sure) but the 4th P/L appeared to be the county line, aka ridge line. At least, that's the way it appears on a plot using ParcelQuest.

But, when I got the deed, I was surprised to read that it was just "the E 1/2 of the E 1/2 of Sec. 11" and didn't even mention the county line, which runs through the middle of the parcel. So, apparently, this parcel sits in both counties. It appears divided on the Assessor's Maps for each county (with separate APNs), but I guess this is only for assessment purposes.

So yeah, I haven't done enough research to know how, or if, any of the parcels would be impacted.

[LS_8750]

Sounds like a perfect boundary description to me. Although a County assessor may not like it.

[land butcher]

Ridge line, center of creek, all worked then.

I too like the aerial idea, in the saddles it would be almost impossible to accurately define the highest point.

Monuments - biggest one there - the ridge line :)