Determination of Floodplain

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mpallamary
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Joined: Tue Mar 11, 2008 2:12 pm

Determination of Floodplain

Postby mpallamary » Tue Mar 23, 2021 4:40 am

A question has come up regarding a land surveyor determining the location of a floodplain. I am not referring to a replotting of FEMA information. Is it permissible for an LS to determine and plot the limits of a floodplain/inundation and plot it?

Thanks all.

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LS_8750
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Joined: Tue Jul 20, 2010 5:36 pm
Location: Sonoma
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Re: Determination of Floodplain

Postby LS_8750 » Tue Mar 23, 2021 11:05 am

In the old days land surveyors ran meander lines. Thoreau was a student of nature. Parcel boundary lines often follow streams, so how does a land surveyor locate the center of a stream? Romantically, you could say yes.

If the LS has the requisite education/training and experience and is willing to take it into the courtroom then knock yourself out.

On the other hand, my education, training and experience in fluvial hydraulics and morphology and surface water hydrology was obtained through engineering, not land surveying.

What sort of floodplain are we talking about? In geomorphology and fluvial hydraulics there are flow thresholds that generate evidentiary events like erosion or sedimentation. Knowing how to read the evidence is key.
Clark E. Stoner, PE, PLS
Bear Flag Engineering, Inc.
Sonoma County
Santa Cruz County
tel. 707.996.8449 (Sonoma) or 831.477.9215 (Santa Cruz)
clark@bearflagcivil.com

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mpallamary
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Re: Determination of Floodplain

Postby mpallamary » Tue Mar 23, 2021 2:59 pm

I think it is an engineering issue and, after an engineer makes the determination, a surveyor can plot it along with other lines as per below:

"building setback lines, flood hazard zones, seismic lines and setbacks, geologic mapping, and archaeological sites."

It is in the context of the SMA and in this case, a flood hazard line:

GOVERNMENT CODE - GOV
TITLE 7. PLANNING AND LAND USE [65000 - 66499.58]
( Heading of Title 7 amended by Stats. 1974, Ch. 1536. )
DIVISION 2. SUBDIVISIONS [66410 - 66499.38]
( Division 2 added by Stats. 1974, Ch. 1536. )
CHAPTER 2. Maps [66425 - 66450]
( Chapter 2 added by Stats. 1974, Ch. 1536. )
ARTICLE 2. Final Maps [66433 - 66443]
( Article 2 added by Stats. 1974, Ch. 1536. )

66434.2.
(a) On or after January 1, 1987, a city or county may, by ordinance, require additional information to be filed or recorded simultaneously with a final or parcel map. The additional information shall be in the form of a separate document or an additional map sheet which shall indicate its relationship to the final or parcel map, and shall contain a statement that the additional information is for informational purposes, describing conditions as of the date of filing, and is not intended to affect record title interest. The document or additional map sheet may also contain a notation that the additional information is derived from public records or reports, and does not imply the correctness or sufficiency of those records or reports by the preparer of the document or additional map sheet.

(b) Additional survey and map information may include, but need not be limited to: building setback lines, flood hazard zones, seismic lines and setbacks, geologic mapping, and archaeological sites.
(Added by Stats. 1985, Ch. 883, Sec. 2.)

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dedkad
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Re: Determination of Floodplain

Postby dedkad » Tue Mar 23, 2021 6:33 pm

Both surveyors and engineers can submit a FEMA Letter of Map Amendment, so I think surveyors do have at least some rights to map a floodplain.


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