Flood Management Amendments
to the Johnson Creek Basin Plan District
FINAL REPORT
Adopted by the Portland City
Council on April 29, 1998
Effective May 13, 1998
Bureau of Planning
Portland, Oregon
April 30, 1998
Johnson Creek Plan District
Flood Management Amendments
Portland City Council
Vera Katz, Mayor
Jim Francesconi, Commissioner
Charlie Hales. Commissioner
Gretchen Kafoury, Commissioner
Eric Sten, Commissioner
Portland Planning Commission
Richard Michaelson, President
Steve Abel, Vice President
Sara [fitch
Amanda Fritz
Rick Holt
Marcy McInelly
Steve Naito
Paul Schubach
Ruth Scott
Final Report
April 30. 1998
To help ensure equal access to information, the City of
Portland Bureau of Planning offers accommodation to
persons with disabilities. Call 823-7700 in advance to
arrange accommodation.
TTY: 823-6868
2
Johnson Creek Plan D;str;ct
Flood Management Amendments
Final Report
April 30, 1998
Flood Management Amendments
to the Johnson Creek Basin Plan District
FINAL REPORT
Acknowledgments
Portland Bureau of Planning
Charlie Hales, Commissioner of Public Safety
David Knowles, Planning Director
Cary Pinard, Chief Planner, Planning Support Group
Project Staff
Tom McGuire, Senior Planner
Bureau of Planning
Portland, Oregon
April 30, 1998
3
Johnson Creek Plan District
Flood Management Amendments
TABLE OF CONTENTS
Background .....
Discussion of Adopted Code Amendments
Planning Commission Discussion ..
Final Report
April 30, J998
6
7
8
Adopted Zoning Code Amendments to Chapter 33.535, Johnson Creek
Basin Plan District 11
Map 535-??: Flood Risk Area and Floodway.
5
................ after page 14
Johnson Creek Plan District
Flood Management Amendments
Background
Final Report
April 30. 1998
Project History
The adopted changes to the Johnson Creek Basin Plan District result from
recommendations from the City of Portland's Development Review Team (DRT). The
DRT is comprised of representatives from the City's development bureaus. It initiated this
effort as a follow-up to the Outer Southeast Community Plan (OSCP). Several of the
OSCP Action Items under the Open Space and Environmental Policy propose that actions
be taken by various City bureaus to address flooding problems along Johnson Creek.
Action Items OS26, OS29, and OS31 are particularly relevant. They are listed below:
0826 Create "balanced cut and fill" regulations for development in the lOG-year
flood plain.
0829 Prepare and implement a comprehensive management approach, including a
Johnson Creek Comprehensive Flood Management Plan, that:
• minimizes or reduces flooding and water quality problems,
• seeks to satisfy multiple objectives, and
• provides for new development safe from flooding impacts.
0831 Rewrite portions of Title 24, Chapters 24.50 and 24.70 to better address
flood impacts from filling and excavation.
The DRT formed a subcommittee in 1996 to follow-up on the direction of the OSCP. The
subcommittee consisted of representatives from the Bureau of Environmental Services, the
Bureau of Buildings, the Planning Bureau, and the City Attorneys Office. Representatives
from the Portland Development Commission and the Bureau of Housing and Community
Development joined later. The subcommittee brought forward the proposed Title 33
amendments to the Johnson Creek Basin Plan District as well as proposed changes to Title
24, after discussions focused on the continual flooding problems in the area of SE Foster
Road and SE 108th in the Lents Neighborhood.
Project Purpose
The purpose of the amendments are to control where and how development can happen in
the floodplain. These code amendments are intended to prevent additional damage caused
by frequent flooding, not to control t1ooding. Other actions are being undertaken by the
City to address t100d reduction issues.
The Johnson Creek Watershed frequently floods, causing property damage, creating a
health and safety hazard to the areas residents, and generating costs to the City for
emergency services. Additional development in frequently flooded areas only compounds
the existing problems. The adopted code changes regulate development in the area most
frequently damaged by flooding-the Flood Risk Area. City staff has delineated the flood
risk area using flood damage surveys, aerial photographs, and modeling. The flood risk
area is shown in Figure I, map 3 of 4. The proposed code changes also modify existing
restrictions in the Floodway, which is also shown in Figure I.
6
Johnson Creek Plan District
Flood Management Amendments
Discussion of Adopted Code Amendments
Title 33-Johnson Creek Basin Plan District
Final Report
April 30, 1998
There were two amendments adopted for the Johnson Creek Basin Plan District.
Restrictions on Redevelopment within the Johnson Creek Floodway
The Plan District previously restricted new above ground structures within the Floodway.
The Federal Emergency Management Agency (FEMA) defines the Floodway as the channel
necessary to allow passage of a IDO-year flood event without raising the flood elevation
more than one foot. Essentially, the F100dway is the active flowing channel during a flood
event. There are some existing structures built within the F100dway on Johnson Creek.
The adopted change limits redevelopment of existing structures in the Floodway.
Expansion of the footprint of all structures in the F100dway is prohibited. Alterations to
industrial and commercial structures within the F100dway that exceed 50 percent of the
assessed value are also prohibited. The level of restriction on new above ground stlUctures
would also be changed from "not allowed" to "prohibited" which means that no adjustment
could be applied for to build within the F1oodway.
Prohibition of Land Divisions and Planned Unit Developments IPUD's2 within the Flood
Risk Area
The policy behind the Flood Risk Area is the reduction of flood damage and loss through
avoidance. The Flood Risk Area covers a large area along Johnson Creek that is frequently
flooded. It is extremely flat and it does not take a very significant precipitation event to
cause some flooding. Additionally, because it is so flat even minor changes in grade, a
new building, or leaves in a storm drain can cause localized flooding and changes in the
flood flow or inundation area.
Within the Flood Risk Area the nooding is not frequent or severe enough to legally justify
prohibiting development of a property outright as in the F100dway but it does warrant an
effort to reduce potential damage by not allowing additional land divisions leading to more
intensive development.
The Bureau of Environmental Services, using records of past nood events, five year flood
event modeling, the 2l0-foot topographic line, and aerial photographs, has delineated an
area found to be frequently nooded. This area is defined as the Flood Risk Area (see
Figure I, map 3 of 4). Because of the risk of property damage, health and safety hazards,
and the costs to the City for emergency services, land divisions and PUD's are prohibited
within the Flood Risk Area. Property owners can maintain existing lots and development
but the current problems inherent to this area should not be increased by allowing further
land division.
7
Johnson Creek Plan District
Flood Management Amendments
Issues
City Council Discussion
Final Report
April 30. J998
The prohibition on alterations of existing: structures exceeding: 50 percent of the assessed
value.
The City Council rejected this restriction for residential properties. The City Council voted
to apply this restriction only to existing commercial and industrial properties. The
prohibition on expansion of a building footprint within the Floodway was adopted for all
zones. The City Council made no other amendments to the Planning Commission's
recommendations
City Council Decision
The City Council took the following actions:
•
•
•
•
adopted the Planning Commission report;
amended the 50 percent impervious surface limitation in the Johnson Creek
Floodplain Subdistrict so that it applies to all zones;
amended the zoning Code to create the Flood Risk Area and adopt the
regulations that prohibit land divisions within the risk area; and
amended the Johnson Creek Floodway standard to prohibit the expansion of
building coverage within the Floodway and to prohibit alterations to existing
commercial and industrial development in the Floodway that exceeds 50 percent
of assessed value.
8
Johnson Creek Plan District
Flood Management Amendments
Final Report
April 30, 1998
Adopted Zoning Code Amendments to
Chapter 33.535, Johnson Creek Basin Plan District
The amendments are shown on the following pages: proposed code language is
shown on the right-hand page, with staff commentary on the left-hand page.
Language to be added is underlined; language to be deleted is shown in
strikethrough.
11
Johnson Creek Plan D,'stn'ct
Flood Management Amendments
Final Report
April 30. 1998
33.535.100 General Development Standards
Adds additional restrictions and thresholds for redevelopment of
structures within the Floodway. Changes the term "not allowed" to
"prohibited" so that the regulation cannot be adjusted.
Prohibits alterations to commercial and industrial structures that exceed
50 percent of assessed value. This change essentially codifies existing
federal requirements.
Johnson Creek Flood Plain Subdistrict Development Standards
33.535.31O.B Impervious surface
Applies the 50 percent impervious surface limitation standard to all
zones. This change was added by the Planning Commission and adopted
by City Council.
33.535.320 Land Divisions and PUDs
Adds a prohibition on land division and PUD's within the "Flood Risk Area".
The Flood Risk Area is illustrated on map. Map 535-1, at the end of the
Plan District Chapter. (see also Figure 1, map j of 4)
12
JohnsDn Creek Plan District
Flood Managemelll Amendments
CHAPTER 33.535
JOHNSON CREEK BASIN PLAN DISTRICT
Final Repm1
April 30. 1998
33.535.100 General Development Standards
The standards of this Section apply to the entire Johnson Creek Basin plan district.
A. "'eeve greund structures The following are not allowed prohibited within the
Johnson Creek F100dway as delineated by the Federal Emergency Management
Agency (FEMA) on July 1, 1991. All eJ;ception Exceptions to this is are fences.
public bridges, outfall structures, and fire hydrants which are allowed subject to
standards set by the Bureau of Environmental Services.
I. New above ground structures;
2. Alterations to existing commercial and industrial structures that exceed 50% of
the assessed value: or
3. Increase of building coverage.
B. through D. [no change]
Johnson Creek Flood Plain Subdistrict Development Standards
33.535.300 Housing Types [no change]
33.535.310 Site Development Standards
A. Tree removal. [no change]
B. Impervious surface. No more than 50 percent of any site in a residential zene
may be developed in impervious surface.
C. Stormwater collection. [no change]
33.535.320 Land Divisions and PUDs
Land divisions and PUDs within the Johnson Creek Flood Risk Area. as indicated on Map
535- I. are prohibited.
13
All data compiled from source materials at different scales.
For more detail, please refer to the source materials or
City 01 Portland, Bureau of Planning.
-------------------
The information on the map was derived from digital data-
bases on the City of Portland, Bureau of Planning GIS. Care
was taken in the emation of this map but it is provided "'as
is", The City of Portland cannot accept any responsibility
for error, omissions, or positional accuracy, and therefore,
there are no warranties which accompany this product.
However, notification of any errors will be appreciated.
Figure 1: Flood Risk Area and Floodway
;
Map 1 of4
Fioodw8Y and Flood Risk Aras: Digitized by BUrB8U of Environ·
mental Services. Source of data and accuracy unknown.
Approximately registered to tax lots.
INFORMATION SOURCES:
Taxlots: Originally produced by Oregon Dept. of Revenue.
Modified and updated by Multnomah County Assessment &
Taxation and Portland Dept. of Transportation. Updated
through April 1998. Accuracy· +/-.1 feet.
April 1996.
Ji
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,
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Johnson Creek Floodway
Flood Risk Area
Scale: 1" = 600'
September 15, 1997
------
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----
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City of Portland
Bureau of Planning
-..
.,
The information an the map was derived from digital data~
basBs an the City at Portland, Bureau of Planning GIS. Care
was taken in the creation at this map but it is provided "as
is". The City of Portland cannot accept any responsibility
for error, omissions, or positional accullICV, and therefore,
there are no warranties which accompany this product.
However, notification of any errors will be appreciated.
All data compiled from source materials at different Bcales.
For more detail, please refer to the source materials or
City of Portland, Bureau of Planning.
~""'-' ....J),
Floodway and Flood Risk Area: Digitized by Bureau of Environ-
mental Services. Source of data and accuracy unknown.
Approximately registered to tax lots.
Taxlots: Originally produced by Oregon Dept. of Revenua
Modified and updated by Muttnomah County Assessment &.
Taxation and Portland Dept. of Transportation. Updated
through April 1996. Accuracy - +1- .1 feet.
April 1996.
~ ~ • ~• •
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.
Johnson Creek Floodway
",""--"~ ".!~;;'::;:j Flood Risk Area
Scale: 1" = 600'
I:;==T-L....."S:-.e"!"p.....tember 15, 1997 _
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::ity of Portland
:lureau of Planning
'.
DMap30f4
All data compiled from Bource materials at different scales.
For more detail, please refer to the source materials or
City of Portland, Bureau of Planning.
The information on the map was derived from digital data-
basss on the City of Portland. Bureau of Planning GIS. Care
was taken in the creation of this map but it is provided "as
is". The City of Portland cannot accept any responsibility
for error, omissions, or positional accuracy. and therefore,.
there are no warranties which accompany this product.
However, notjfication of any errors will be appreciated.
Floodway and Flood Risk Area: Digitized by Bureau of Environ-
mental Service&. Source of data and accuracy unknown.
Approximately registered to taxlots.
Tsxlots: Originally produced by Oregon Dept. of Revenue.
Modified and updated by Multnom8h County Assessment &.
Taxation and Portland Dept. of Transportation. Updated
through April 1996. Accuracy - +/-.1 feet.
April 1996.
~.:.::~~I:'::::'::;j Flood Risk Area
Scale: 1" = 600'
January 02, 1998
L.JL....J"L-_ ... .. _
<
---===~-'=ft---r:Prl.~l¢:A=:81ITID ~G NO
~=-'---L:-r-:lTTtl~ ~ fi I Johnson Creek Floodway
~ity of Portland
lureau of Planning
'.
....., "!'
All data compiled from source materials at different Bcales.
For more detail, please refer to the source materials or
City of Portland, Bureau of Planning.
The information on the map was derived from digital data-
basBs on the City of Portland, Bureau of Planning GIS. Care
was taken in the creation of this map but it is provided "as
is", The City of Portland cannot accept any responsibility
for error, omissions, or positional accuracy, and therefore.
there are no warranties which accompany this product.
However, notification of any errors will be appreciated.
Figure 1: Flood Risk Area and Floodway
Map40f4
Floodway and Flood Risk Area: Digitized by Bureau of Environ-
mental Services. Source of data and accuracy unknown.
Approximately registered to taxlots.
Taxlots: Originally produced by Oregon Dept. of Revenue.
Modified and updated by Multnomah County Assessment &
Taxation and Portland Dept. of Transportation. Updated
through April 1996. Accuracy - +/-.1 feet.
April 1996.
INFORMATION SOURCES:
Scale: 1" = 600'
September 15, 1997
LEGEND
~illl~\!\ Johnson Creek Floodway
f..:-.:-::::~
I::::':"::::J Flood Risk Area
;
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ow,
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City of Portland
Bureau of Planning