California Surveyors Forums

How do you find the mean high tide line in a given area along the coast?

It depends. There are some experts here, like Evan Page, who hopefully will chime in, but this is a tool you should have in your tool kit:

http://vdatum.noaa.gov/

And a recorded webinar about the tool:

http://www.ngs.noaa.gov/corbin/class_de ... ATUM.shtml

I read Flushman's "Water Boundaries" a few years ago and learned that you need to be prepared for absolute Hocus Pocus. The Courts are blind and so are the professionals, because the evidence does not exist based on ancient case precedence.

Remember, lawyers write books to gain clients. Just like everybody else.

The rules are one thing, litigated. The application of the rules are another... Subject to a bullshit call by somebody that has a sense of practicality.

Thanks! This NOAA site looks pretty complex. Being new to this, I was hoping it would be a simple thing. For example, at this particular beach, the MHW is some given elevation. Is there a clean database that displays this info or is this far more involved of a question?

Unless your project location is immediately adjacent to a tidal bench mark that also has a geodetic (orthometric) elevation on it, some level of interpolation or modeling will be involved to determine the relationship between the tidal datum and geodetic datum (like NAVD88) at you location of interest. VDATUM can compute this relationship based on the model for a specific latitude and longitude (input by the user). Watch the webinar and read the VDATUM related materials on the NGS website. If you are going to do this type of specialize work, you need to educate yourself or you are not practicing in your area of competency.

Here are a few links from the Orange County Surveyor's website...some good info...

Procedures for establishing the Mean High Water line boundaries
http://ocpublicworks.com/civicax/fileba ... lobID=8453

Orange County Tideplanes and Tidal Datum relationships
http://ocpublicworks.com/civicax/fileba ... lobID=8451

US Tidal Datum Relationships with Marine boundaries
http://ocpublicworks.com/civicax/fileba ... lobID=8470

Thanks again for all the info. I've done a topo of the beach front condos and sea wall but am not under contract to determine this part. It's definitely out of my area of competency. Is there anyone out there familiar with this process that would be interested in taking this on? Feel free to send me a message.

The Orange County Public Works documents Ryan posted are a bit dated (current tidal epoch is 1983 - 2001, not 1960-1978), but the procedure is what I would describe for a shoreline unaffected by artificial influence.

I differ with their method for areas affected by artificial influence in that they recommend using the meanders of the parcel as it was originally described, or using those of the most recent record map prior to the introduction of the artificial influence. I'll qualify that advice by stating that sometimes, such a record map or the original description are the best evidence of the last natural location. The author of that document states that in his experience, such a record map is the best info available.

In my experience, a record map is the best evidence about half of the time. Sometimes the best evidence will be topographic mapping by the US Coast Survey (later, the USC&GS). In some locations, the MHTL had been mapped by the county surveyor at various times, or mapped by the State Lands Commission. Each one of those mapping efforts is a snapshot in time, but generally, the one that is nearest in time prior to the introduction of the artificial influence, and wherein proper procedures were used to locate the MHTL, will be most reliable.

I've found that quite often, an incorrect elevation had been used in determining the MHTL location on filed maps. Not always, but in my experience, it is the case perhaps about 30% of the time. It's something one should check before relying on the line identified on a record map.

Depending upon your specific location, State Lands may have had the need to identify the last natural location of the MHTL. When and where that has occurred, the resulting MHTL location is likely to have been determined after considering a broader set of records and data than most private surveyors will have considered, either due to expediency or due to fewer resources readily available to the surveyor.

Clark's take is quite cynical, but there is some truth to it. First off, if the shore is in a natural state and still a legally ambulatory boundary, depending upon the shoreline material, it's likely to move anywhere from several feet to over 100' in a given year (unless the shore is a rock face). Being a snapshot in time, the MHTL you locate may be anywhere within that tidal shoreline fluctuation range. The time of year you do the field work on the shore can and likely will affect the location greatly.

When trying to determine the last natural location, you are relying on the records available to you and possibly on physical evidence (though far more often on records). In doing so, you are looking at various snapshots in time. If you investigate the tide level records from when the work was done, you may be able to get some idea of where within the shorelines normal fluctuation range the line per that record is. If they don't state a method, they may have simply located the water's edge as the rodman walked down the beach and you really have no idea whether it represents a daily high water line, low water line, or some random location between. On the records you deem to be reliable, you're making a best estimate. So with the technical means of determining, there is consideration of law, weighing of the technical reliability of the data available to you, and varying measures of guesswork (i.e. hocus-pocus), depending on the data you have.

On the legal side, the rules of what the boundary is have been developed, for the most part, based on common sense and a general balancing of equities between landowners in particular disputes, and between private landowners and the rights of the general public. Thompson v. Teschmacher being a notable exception (application of the neap tide rule), the majority of published case law makes sense in a conceptual way. The technical aspects of putting those principles into effect is where the "hocus-pocus" enters.

As to your original question, I'm beginning to stray into the tules. For the technical, on-the-ground-process, follow that outlined in the OC document, which is similar to what NOAA/NOS suggests.

If you are working in a bay or estuary, extra care is required. In that case, feel free to call or contact me and I can either email some materials or provide additional explanation.

Thanks Evan for sharing. Luckily, this project only has to do with the design of a sea-wall, not property lines! I've learned that there is a tidal station with orthometric elevation about 1.2 miles from the site. Maybe it's not so complex, don't know, but I've got someone else here locally to make the determination, so I'm off the hook!