1. can someone please explain the difference between the mean high water line and the Seasonal High Water (SHW) line?
2. I've also recently heard of a quick computation to determine the Seasonal High Water (SHW) line, from the mean high water line. If anyone has this or can explain, please help.
3. which would hold, the mean high water line established by the state or the Seasonal High Water (SHW) line?
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TY!!!!
"Mean high water" is a measurement of where the water line of a body of water (sea, ocean, lake, or river) intersects uplands.
"Seasonal high water" is a measurement of the water table on dry land usually done through boreholes. It's not a water line measurement in the same way as MHW.
MHW/OHW (or MHHW or MLLW depending on state) are used to define legal boundaries.
I've never heard of SHW defining the (horizontal) extent of a parcel. For landlocked parcels, the water table is a plane existing below the surface, and does not intersect it (hence the measurement of SHW by borehole).
I guess there could be an oddball situation, but generally as soon as the water table intersects the ground surface with any consistency, it would be classified as a water body and thus subject to the typical OHW/MHW designations.
Anyone know of a case where the SHW was designated as a horizontal boundary?
Apples and oranges. MHW applies to tidally influenced waters, typically determined relative to a tidal datum and OHW, non tidal, typically the marked by a change in vegetation. Seasonal must be regional because other the than a base flood elevation, never heard of it outside of ground water relating to septic systems and the like. So, all very different things.
Mean Annual High Water is also evaluated for non-tidal rivers and streams in Mass. It pertains to restrictions under the state River Protection Act. We often have to locate MAHW flagging after a wetland specialist has gone through and made a determination.
