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[IowaAPA] FEMA DFIRM -- New A Zones

L

Laura Carstens

Guest
The City of Dubuque has received a draft Digital Flood Insurance Rate Map (DFIRM) from FEMA that includes several new A zones.

The new DFIRM significantly expands the number of properties designated as being in a flood plain in the city limits. There are approximately 70 structures in the current flood zones. The proposed new A zones would include approximately 1,806 properties, with an estimated 1,741 structures.

We are interested to learn if any other cities or counties in Iowa are encountering similar changes in their DFIRMs with respect to new, substantial A zones.

If your DFIRM did not change, we'd like to know that, too.

We look forward to hearing from you. Thanks!

Laura Carstens




Laura Carstens
Planning Services Manager
50 W. 13th Street
Dubuque IA 52001
Phone: 563-589-4210
Fax: 563-589-4221
 
B

Burke, Bill

Guest
The same thing (errors) occurred on the Lansing FEMA maps. In this case, the FEMA consultant I talked with acknowledged using 1960's era 20 foot contour mapping-no wonder.
Also, I have found several such map differences in communities in Wisconsin which I work with.
Bill Burke AICP

From: IowaAPA (AT) yahoogroups (DOT) com [mailto:IowaAPA (AT) yahoogroups (DOT) com] On Behalf Of Laura Carstens
Sent: Tuesday, November 03, 2009 10:52 AM
To: IowaAPA (AT) yahoogroups (DOT) com
Subject: [IowaAPA] FEMA DFIRM -- New A Zones

The City of Dubuque has received a draft Digital Flood Insurance Rate Map (DFIRM) from FEMA that includes several new A zones.

The new DFIRM significantly expands the number of properties designated as being in a flood plain in the city limits. There are approximately 70 structures in the current flood zones. The proposed new A zones would include approximately 1,806 properties, with an estimated 1,741 structures.

We are interested to learn if any other cities or counties in Iowa are encountering similar changes in their DFIRMs with respect to new, substantial A zones.

If your DFIRM did not change, we'd like to know that, too.

We look forward to hearing from you. Thanks!

Laura Carstens



[cid:image001.jpg (AT) 01CA5C7F (DOT) 484B5920]
Laura Carstens
Planning Services Manager
50 W. 13th Street
Dubuque IA 52001
Phone: 563-589-4210
Fax: 563-589-4221
 

erinc

Member
Messages
1
Points
0
The City of Newton (IA) had the same experience. They took former Zone B areas, expanded them and then made them Zone A. There was one area in particular that they were so far-off that we were eventually able to get them to pull the zone back. It was a very frustrating process with eventually led to the involvement of some politicians.

Newton did not have a BFE completed for the City. The FEMA consultants/technicians doing the DFIRM were using topography maps and aerial photographs to make their determination. In this one particular location, if a site visit had been completed, it would have been quite clear that the need for the very large designated zone was not necessary. Unfortunately, a site visit on the part of FEMA or their contractor was never completed.


If you are interested, I would be glad to scan some of the correspondence between the City and FEMA for you to take a look at. Feel free to email me at erinc@newtongov.org if you have any questions.

Erin R. Chambers, AICP
City Planner, City of Newton
1700 N 4th Ave W
Newton, Iowa 50208
641-792-6622
erinc@newtongov.org
 
L

Laura Carstens

Guest
Thanks, Bill.

>>> "Burke, Bill" <bburke (AT) davyinc (DOT) com> 11/3/2009 12:15 PM >>>

The same thing (errors) occurred on the Lansing FEMA maps. In this case, the FEMA consultant I talked with acknowledged using 1960's era 20 foot contour mapping-no wonder.
Also, I have found several such map differences in communities in Wisconsin which I work with.
Bill Burke AICP

From: IowaAPA (AT) yahoogroups (DOT) com [mailto:IowaAPA (AT) yahoogroups (DOT) com] On Behalf Of Laura Carstens
Sent: Tuesday, November 03, 2009 10:52 AM
To: IowaAPA (AT) yahoogroups (DOT) com
Subject: [IowaAPA] FEMA DFIRM -- New A Zones

The City of Dubuque has received a draft Digital Flood Insurance Rate Map (DFIRM) from FEMA that includes several new A zones.

The new DFIRM significantly expands the number of properties designated as being in a flood plain in the city limits. There are approximately 70 structures in the current flood zones. The proposed new A zones would include approximately 1,806 properties, with an estimated 1,741 structures.

We are interested to learn if any other cities or counties in Iowa are encountering similar changes in their DFIRMs with respect to new, substantial A zones.

If your DFIRM did not change, we'd like to know that, too.

We look forward to hearing from you. Thanks!

Laura Carstens




Laura Carstens
Planning Services Manager
50 W. 13th Street
Dubuque IA 52001
Phone: 563-589-4210
Fax: 563-589-4221
 

The One

Cyburbian
Messages
8,283
Points
29
Hmmm.....

I'm not in Iowa, but......

Are the newly shown Zone A's being converted from previous shaded zone x areas? If so, were these previous shaded zone x areas in place due to provisionally accredited levees? Are the levees now being decertified (like those along the Colorado River)?

I think the biggest problem area in Western Arizona with similar issues is near the community of San Luis. 1,000's of homes in a shaded zone x that may now be within a zone A or D after Colorado Levees are decertified. I just checked and their PAL agreement with FEMA is set to expire in 16 days:-c having two+ years of notice helped provide the residents with the time needed to buy the lower priced insurance policies and to be considered as pre-existing policy holders.
 
L

Laura Carstens

Guest
The largest of the new A zones, impacting 1,400 properties, has never been on a FIRM in any kind of zone.

We have a levee/floodwall system along our Mississippi Riverfront that we are in the process of certifying with the help of the U.S. Army Corps of Engineers in accordance with our PAL with FEMA. The levee provides Zone X coverage for a large portion of our downtown, industrial waterfront areas, and commercial recreational areas.



Laura Carstens
Planning Services Manager
50 W. 13th Street
Dubuque IA 52001
Phone: 563-589-4210
Fax: 563-589-4221


>>> Cyburbia Forums Gateway <gateway.iowaapa (AT) cyburbia (DOT) org> 11/3/2009 3:47 PM >>>


I'm not in Iowa, but......

Are the newly shown Zone A's being converted from previous shaded zone
x areas? If so, were these previous shaded zone x areas in place due to
provisionally accredited levees? Are the levees now being decertified
(like those along the Colorado River)?

I think the biggest problem area in Western Arizona with similar issues
is near the community of San Luis. 1,000's of homes in a shaded zone x
that may now be within a zone A or D after Colorado Levees are
decertified. I just checked and their PAL agreement with FEMA is set to
expire in 16 days:-c having two+ years of notice helped provide the
residents with the time needed to buy the lower priced insurance
policies and to be considered as pre-existing policy holders.


--
The One

Stephen King's inspiration:
While browsing through an attic with his elder brother, King uncovered
a paperback version of an *H. P. Lovecraft *collection of short stories
that had belonged to his father. The cover art-an illustration of a
monster hiding within the recesses of a hell-like cavern beneath a
tombstone-was, he writes, "the moment of my life when the dowsing rod
suddenly went down hard ... as far as I was concerned, I was on my way."
------------------------------------------------------------------------
The One's Profile: http://www.cyburbia.org/forums/member.php1989
View this thread: http://www.cyburbia.org/forums/showthread.php?t=39281



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The One

Cyburbian
Messages
8,283
Points
29
Ok...

Assuming the levee certification is successful, the previously shaded zone x should remain a zone x for the area protected by the now certified levee and depicted as such on the new maps. If the levee certification is unsuccessful, the previously shaded zone X area could be shown as Zone D or A on the new maps.

A truly new zone A area not associated with the levee system may be related to some other flood consideration.

Are the maps showing new Zone A areas labeled as preliminary DFIRMS for your jurisdictional review and comment?
 
P

Paul Dekker

Guest
The City of Urbandale has a similar experience with the draft DFIRM
issued in June (still "pending"). Existing Zone A's were impacted by
substituting "new" topographic information with 10-foot contour
intervals (I think) for the City's old, but 2-foot contour maps that had
been utilized by FEMA for all prior FIRMS and which continues to be used
for one waterway with a detailed study.

Engineering consultants retained by the City in the early 1980's used
the same topographic information, supplemented by field measurements of
culverts and limited cross-sections, to largely affirm the Zone A
boundaries of the FEMA maps.

The "new" topo used by FEMA's consultant on the DFIRM, because of its
far less-precise contour interval, takes in substantially more
structures and some additional properties-not because of better flood
studies or information substantiating flood risks that hadn't previously
been identified, but because of less precise mapping. The DFRIM has
MUCH better horizontal control, given that the old FIRM's had none, but
it's "false accuracy".

There was also one new Zone A established that takes in numerous
properties, that hadn't previously been identified. It's reasonable
that the Zone A was identified, since its basin is equal to that of
other Zone A's, BUT it also utilized imprecise topo information that
grossly overstates the flood hazard. The area was developed with
engineered channels sized to carry the 1% storm, but the Zone A was
established as if everything had remained pre-development in terms of
the stream, but post-development in terms of runoff (and disregarding
storm detention).

Within detailed study areas, there is some imprecise mapping because the
"hard copy" boundaries were overlaid on the DFIRM without any "rubber
sheeting" to account for discrepancies between the accurate horizontal
scaling of the DFIRM and very imprecise scale of the "hard copy" FIRM.
(The old FIRM's are not only at a very small scale, but imprecisely
drawn so that map-scaled dimensions between fixed points deviate by 10%
or more from actual, verifiable dimensions. The DFIRM's are close to
the actual, verifiable dimensions BUT when the old "hard copy" zone
boundaries were overlaid onto the DFIRM they weren't adjusted to account
for the DFIRM's change in horizontal accuracy, to maintain the same
relationship between zone boundary and fixed points that existed on the
FIRM.) Optimally, accurate topography would have been used instead of
overlaying the old zone boundaries at all, so flood limits wouldn't run
uphill, etc. but if the old lines HAD to be used they should at least
have been adjusted.

Urbandale wasn't allowed to "object" since no new Base Flood Elevations
were issued for the community, and was therefore limited to "comment".
"Comment" were filed per the above in July (use the City's 2-foot
contours/engineering studies in lieu of the 10-foot contours etc), with
no response received to date.

Optimally, the State's LiDAR would be used to the maximum extent
possible, which would VASTLY improve the DFIRM over anything prior, even
without any new studies, in my opinion....



Paul Dekker



Director of Community Development

3600 86th Street

City of Urbandale, IA 50322-4057



515-331-6721

515-278-3927 (Fax)

PDekker (AT) Urbandale (DOT) org

http://www.urbandale.org/



________________________________

From: IowaAPA (AT) yahoogroups (DOT) com [mailto:IowaAPA (AT) yahoogroups (DOT) com] On Behalf
Of Laura Carstens
Sent: Tuesday, November 03, 2009 10:52 AM
To: IowaAPA (AT) yahoogroups (DOT) com
Subject: [IowaAPA] FEMA DFIRM -- New A Zones



The City of Dubuque has received a draft Digital Flood Insurance Rate
Map (DFIRM) from FEMA that includes several new A zones.



The new DFIRM significantly expands the number of properties designated
as being in a flood plain in the city limits. There are approximately
70 structures in the current flood zones. The proposed new A zones
would include approximately 1,806 properties, with an estimated 1,741
structures.



We are interested to learn if any other cities or counties in Iowa are
encountering similar changes in their DFIRMs with respect to new,
substantial A zones.



If your DFIRM did not change, we'd like to know that, too.



We look forward to hearing from you. Thanks!



Laura Carstens









Laura Carstens

Planning Services Manager

50 W. 13th Street

Dubuque IA 52001

Phone: 563-589-4210

Fax: 563-589-4221
 
L

Laura Carstens

Guest
Yes, the Zone X will remain as a protected area.

Yes, the maps showing new Zone A areas are labeled as preliminary DFIRMS for
your jurisdictional review and comment.





Laura Carstens
Planning Services Manager
50 W. 13th Street
Dubuque IA 52001
Phone: 563-589-4210
Fax: 563-589-4221


>>> Cyburbia Forums Gateway <gateway.iowaapa (AT) cyburbia (DOT) org> 11/3/2009 5:22 PM >>>


Assuming the levee certification is successful, the previously shaded
zone x should remain a zone x for the area protected by the now
certified levee and depicted as such on the new maps. If the levee
certification is unsuccessful, the previously shaded zone X area could
be shown as Zone D or A on the new maps.

A truly new zone A area not associated with the levee system may be
related to some other flood consideration.

Are the maps showing new Zone A areas labeled as preliminary DFIRMS for
your jurisdictional review and comment?


--
The One

Stephen King's inspiration:
While browsing through an attic with his elder brother, King uncovered
a paperback version of an *H. P. Lovecraft *collection of short stories
that had belonged to his father. The cover art-an illustration of a
monster hiding within the recesses of a hell-like cavern beneath a
tombstone-was, he writes, "the moment of my life when the dowsing rod
suddenly went down hard ... as far as I was concerned, I was on my way."
------------------------------------------------------------------------
The One's Profile: http://www.cyburbia.org/forums/member.php1989
View this thread: http://www.cyburbia.org/forums/showthread.php?t=39281



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Queen B

Cyburbian
Messages
3,179
Points
24
I am not in Iowa either but the City of Salina, KS is experiencing the same thing. They have a significant number of homes being put in the Zone A. If they don't get levy accredidation then almost the entire city proper will be in.


Being the good CFM that I am, I checked to make sure we were out of the floodplain. But alas in the new maps we are in. We have done some extensive "landscaping";);) and intend to file a LOMA as soon as the new maps are adopted.
 
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