HomeMy WebLinkAboutRes1996-039
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Sponsored by: Garzini
CITY OF SEWARD, ALASKA
RESOLUTION NO. 96-039
A RESOLUTION OF THE CITY COUNCIL OF THE CITY
OF SEWARD, ALASKA, ADOPTING THE SEWARD FLOOD
HAZARDS MITIGATION PLAN
WHEREAS, severe September 1995 flooding in the Seward area resulted in substantial
public and private property damage; and
WHEREAS, disaster declarations by the City of Seward, Kenai Peninsula Borough, State
of Alaska and the President of the United States enabled the City to receive federal disaster relief;
and
WHEREAS, the State of Alaska Division of Emergency Services (ADES) and Federal
Emergency Management Agency (FEMA) require that a flood plain mitigation plan be completed
and adopted before the City will be eligible to apply for Federal Section 404 Flood Hazard
Mitigation Grant funding; and
WHEREAS, FEMA and ADES have set the first week of March to receive an approved
flood hazard mitigation plan targeting repetitive loss areas; and
WHEREAS, the ADES has received the draft plan and will accept a formal adoption at a
later date; and
WHEREAS, "Flood Mitigation Planning" is Number 3 on the City's adopted Legislative
Priority List as set forth in City of Seward Resolution No. 95-153;
NOW, THEREFORE, BE IT RESOLVED BY THE CITY COUNCIL OF THE CITY
OF SEWARD, ALASKA, that:
Section 1. The Seward Flood Hazards Mitigation Plan, attached and incorporated herein
by reference, is approve.
Section 2. The Seward Flood Hazards Mitigation Plan will be forwarded to the Alaska
Division of Emergency Services to meet Flood Hazard Mitigation Grant funding prerequisite.
Section 3. This resolution shall take effect immediately upon its adoption.
PASSED AND APPROVED by the City Council ofthe city of Seward, Alaska, this 18th
day of March, 1996.
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FLOOD HAZARDS MITIGATION PLAN
Prepared by:
City of Seward
Community Development Department
with
Hensley Consulting Services
1996
SEWARD FLOOD HAZARDS MITIGATION PLAN
TABLE OF CONTENTS
INTRODUCTION .............................................................. 1
COMMUNITY PROFILE ........................................................ 3
GENERAL FLOODING HISTORY ............................................... 5
WATERSHED DESCRIPTION
FLOODING, MITIGATION AND RECOMMENDATIONS. . . . . . . . . . . . . . . . . . . 8
Spruce Creek. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Lowell Creek. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10
Rudolph (Scheffler) Creek ................................................ 15
Jap(anese) Creek ........................................................ 17
Resurrection River Basin ................................................. 20
Sawmill Creek .......................................................... 23
Fourth of July Creek ..................................................... 23
OTHER ISSUES AND MITIGATION RECOMMENDATIONS ............ . . . . . . . . . . 27
CONCLUSION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
APPENDIX ................................................................... 31
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Figure 1. General Seward Location Map
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INTRODUCTION
Authority
The City of Seward has prepared this Flood Hazards Mitigation Plan in compliance with
Federal Emergency Management Agency (FEMA) and Alaska Division of Emergency
Services (A DES) hazard mitigation grant funding eligibility requirements of the Robert T.
Stafford Disaster and Emergency Assistance Act (Public Law 93-288, Section 409). Both time
and budget constraints preclude acquisition of detailed engineenilg or field data for
conclusive development of project costs and design when addressing mitigation measures.
Coordination
Because of the multi agency jurisdictions involved, the Kenai Peninsula Borough (KPB) has
agreed to assume the lead role in discussing and coordinating Resurrection River mitigation
efforts. Although the river is addressed here detail work will be found in the borough's
planning efforts. The City and KPB have been closely coordinating both flood hazards
mitigation planning efforts.
Purpose
While the city's 1985 Comprehensive Plan and 1991 Update (Appendix) provide some overall
direction regarding flood hazards, this plan will serve as a more definitive guide for local,
state, federal and private entities. It identifies areas subject to repetitive flooding and
assesses the flood hazards in those areas. Recommended mitigation alternatives target
reducing long-term flooding risk. Although the plan is narrow in scope, covering only
flood hazards, it is the foundation for an overall City of Seward All Hazards Mitigation Plan.
Goals
The City of Seward was founded and has developed upon alluvial fans and fan-deltas
formed at the mouths of steep tributary valleys to Resurrection Bay. The principal goal of
hazard mitigation within the city is the prevention of loss of life and protection of public and
private development.
Seward Flood Hazards Mitigation Plan
THE PLANNING PROCESS
Over the past fifteen years there have been many studies and reports written concerning
flooding problems in Seward. Many meetings and public hearings have been conducted
concerning the subject. It is clear that the citizens of the City understand the problems
intimately, and are now anxious for mitigation results.
During the preparation of this report it was discussed with interested citizens, and a public
hearing was held in cooperation with the Kenai Peninsula Borough to seek information and
ideas. The following is a synopsis of public comments:
"We understand the problems. Mitigation needs to begin."
"They say the Lowell Creek tunnel problem is too costly to mitigate. What is a
human life worth? Lives will be lost if the tunnel plugs or fails."
"All the Corps of Engineers wants to do are conduct studies, not help with actual
solutions."
"All we hear is why things can't be done, and nothing on what can be done."
"We want, and must help ourselves. But, the problems are too big for us or other
agencies to solve. We will need money from both the Federal and State
governments."
"If all agencies, and the City, would cooperate more and spread out the costs, we
could do some things."
"It seems few care about the seriousness of Seward's flooding problems. Nothing is
done unless there is a disaster. How big a disaster will it takes to get some real
mitigation."
This flood mitigation plan was formally approved by the City of Seward Planning and
Zoning Commission on March 3, 1996; and by the Seward City Council on March 18, 1996.
Seward Flood Hazards Mitigation Plan
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COMMUNITY PROFILE
The City of Seward is located at the head of Resurrection Bay on the Kenai Peninsula, 125
highway miles south of Anchorage. It possesses the only ice-free port in Alaska with road
and rail connections to the state's interior. Seward's economy, traditionally based on its role
as the ocean terminus of the Alaska Railroad, has diversified in recent years.
Seward's economic future is bright because the city possesses several attributes usually not
found in combination in Alaska:
It year-round road, railroad, air, and water accessibility;
It central location to maritime traffic;
It proximity to Anchorage, Alaska's largest city;
It availability of labor and labor training facilities;
It open and accessible topography;
It supporting public infrastructure; and
It ice-free port facilities.
The Seward's economic development activity reflects its diversity. The community offers
complete emergency and maintenance ship repair facilities for ships up to 350 feet in length
at the Seward Marine Industrial Center (SMIC).
Four seafood processing companies operate plants in Seward. The community supports the
fishing industry by providing supplies, ship repair, chandlery, and marine electronics
services.
Bulk and general cargo activity includes the annual shipment of approximately 800,000 tons
of export coal to South Korea from Seward's bulk commodity loading terminal. In addition,
the Port of Seward handled more than four and one half million board feet of logs and 78
thousand tons of miscellaneous cargo during 1995.
Education is a key contributor to the local economy. In addition to the public school system,
the Alaska Vocational Technical Center (A VTEC) is the State's resident vocationaVtechnical
school. Individuals from across the State attend the school to be trained for skilled jobs.
Seward is also the home for the University of Alaska's Institute of Marine Science, Seward
Marine Center (IMS) an important research facility for oceanographic studies. The institute
operates the research vessel Alpha Helix from Seward.
During 1995, site preparation, utilities and a sea wall were constructed in anticipation of 1996
work to begin construction of the Alaska SeaLHe Center. It will be built next to the IMS
facility on the waterfront at the south end of town. The Sea Life Center will be a nationally
Seward Flood Hazards Mitigation Plan
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recognized research facility to further understanding of marine mammals and birds. Teams
of researchers will work to improve the world's fisheries to sustain this vital food supply for
future generations.
The Center will also include a visitor component. Most marine theme parks and aquariums
are designed to entertain. In contrast, the Alaska Sea Life Center will actively engage visitors,
create awareness of marine ecosystems, and foster environmental stewardship. Rookeries
and other marine habitat areas will introduce visitors to the diversity of life forms that live
in our oceans. It is expected that more than 250,000 people will visit the Sea Life Center each
year.
With more than 200, 000 visitors making Seward a destination, tourism and recreation is
growing rapidly. Cruise ship port calls increased from 39 in 1990 to 106 in 1995. Other
activities drawing visitors to Seward include; sport fishing, boating, snowmobiling,
sightseeing, charter tours to Kenai Fjords National Park and Prince William Sound. Hiking,
camping and visits to glaciers and scenic views are also popular.
Figure 2. Detailed Location Map of Seward
Seward Flood Hazards Mitigation Plan
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GENERAL FLOODING HISTORY
This, and the sections which follow, are based on recent information derived from the flood
of September 1995 and liberal use of the listed references.
In 1903 the City of Seward was founded on the Lowell Creek alluvial outwash fan. Since
then it has expanded upon other alluvial fans and fan-deltas formed at the mouths of steep
tributary valleys to Resurrection Bay. Resurrection River has contributed the largest fan.
Four smaller fans are formed by Fourth of July, Japanese, Lowell, and Spruce Creeks.
Geologic and hydrologic characteristics of alluvial fans create particular hazards for
development. These fan-shaped deposits of rock and soils are formed by material eroded
from steep valley walls and deposited at the valley floor. Many of the tributary valleys in
Seward are flanked with moraines (silts, sand and gravel) deposited by retreating glaciers
and are highly susceptible to erosion.
Stream channels on alluvial fans tend to be unstable, as sediments and debris block one
channel and the stream flow cuts others. Development on any portion of a fan is susceptible
to flooding and erosion as this process is repeated.
The problems are more pronounced in periods of heavy rainfall and rapid snowmelt as
runoff saturates the material on the steep valley walls, causing slope failure. The material
is carried downhill, gaining velocity and more debris. In some instances, debris and rock
avalanches form a temporary dam blocking a stream flow and later releasing a flood of
water and material.
Problems are also caused by channel migration. Alluvial fans form as stream channels
migrate across the ground surface, often changing course drastically during large floods. As
a result, the entire surface of the fan apron is subject to flooding at any given time, and a
single flood zone across the fan cannot be delineated.
The Seward area has a history of flooding. However, the severity has increased significantly
over the past 30 years. A great deal of residential and commercial development has occurred
on the fans. More buildings encroach upon stream beds. Roads and bridges become barriers
to efficient water movement. Significant storm events causing serious flooding within the
past 10 years have occurred in October 1986, August 1989 and September 1995.
The Flood of October 9-11, 1986 was the resuLt of a large North Pacific storm system
which moved onshore over Southcentral Alaska. There, it caused record-setting rainfall that
led to widespread, catastrophic flooding and land slides. One of the hardest-hit areas was
the City of Seward, which received more than 15 inches of rain in one 24-hour period. Broad
Seward Flood Hazards Mitigation Plan
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areas along the Resurrection River and Salmon Creek at the head of Resurrection Bay were
inundated. Effects of the floodwaters were exacerbated by severe erosion and subsequent
deposition of rock and debris along the channels of steep mountain streams. The high
sediment discharge, combined with trees, brush and other debris, clogged channels at
bridges and culverts causing overtopping and erosion of bridge approaches and railroad and
highway embankments; interruption of road and rail transportation; and destruction and
damage to businesses and residences.
The intense rainfall saturated steep slopes along the mountain streams, inducing landslides,
avalanches, and debris flows that contributed material to debris-laden solids and in some
instances temporarily dammed stream channels. The sudden failure of these debris dams
resulted in mass movement of earth, rock, vegetation, and water. This surge-release
flooding produced peak discharges substantially greater than any previously determined
flood flows.
While the rainfall frequency for the October 1986 storm was on the order of the 1oo-year
flood event, the flood frequency for the affected streams may be more or less than the 100-
year event. There is evidence that numerous incipient land slides developed as a result of
the storm but did not release. Future storms could release these land slides which would
cause ponding, and eventually surge flooding.
As a result of an August 1989 storm, the Seward area experienced a localized flood event
that received a state, but not federal disaster declaration. Damage in the area amounted to
over $1 million to homes, roads and bridges. As in the 1986 flood, damage within the city
was principally to public infrastructure.
The September 1995 flood was caused by heavy rains associated with Typhoon Oscar.
Total rainfall exceeding 14 inches, of which 10 inches fell in two days, saturated the Seward
area. Streams overflowed their banks damaging public infrastructure in the city and many
homes in the outlying Bear Creek area. Roads and bridges throughout the area were
washed out and damaged, as was the airport and harbor.
The intensity of the storm was slightly less than the 1986 event, but again, the severity of
the flooding varied from drainage to drainage. Resurrection River was considered a 25 year
flood event while Lowell Creek measured as a 10 year event. To some extent this had to do
with high altitude warming that added mountain snowmelt to the rainfall.
A major difference was the creation of flood water diversions, sedimentation changes and
river channel diversion on the Resurrection River. Flooding damage from creeks such as
Spruce, Japanese and Sawmill was different and less severe, in part due to the mitigation
measures such as the levees constructed after the 1986 and 1989 storms.
Seward Flood Hazards Mitigation Plan
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FIGURE 3
SEWARD AREA, 1986 FLOODED AREAS.
1995 FLOODED AREAS & FIRM ZONE A
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WATERSHED DESCRIPTION
FLOODING, MITIGATION AND RECOMMENDATIONS
This section provides an examination of individual watersheds that drain through the City
to Resurrection Bay. This includes the effects of flooding in recent years, along with
mitigation measures accomplished after the 1986 and 1989 floods and their effectiveness
during the 1995 storm. Finally, additional mitigation needs are addressed.
*Spmce Creek
Spruce Creek drains a 9.26 square-mile watershed. Less than one-quarter of the watershed
is vegetated, and approximately 8 percent is covered by glacier. The creek flows into
Resurrection Bay approximately 2 miles south of Seward at Lowell Point which lies at the
end of the road on the bay's west side. Although the Spruce Creek drainage is outside the
city limits, in additon to both residential and commercial buildings, the City sewer lagoon,
associated sewer and electric lines and the Spruce Creek Bridge are located here. This vital
infrastructure must be protected.
Flooding History
A small lake formed by perennial snow within the headwaters of Spruce Creek presents a
potential for surge-release flooding. The braided distribution channels on the lower areas
of the creek are evidence of random shifting of stream courses that take place on the distal
parts of an alluvial fan.
The intense rainfall causing the 1986 flood triggered a massive debris avalanche on the steep
northern slope of Spruce Creek 0.8 miles above its mouth. The mass of debris deposited in
the channel was 1,000 feet long and 200 feet wide, which caused damming and short-term
storage of water, earth, rock and trees. The breaching of the dam released a water-debris
slurry which was rapidly transported downstream. All the debris avalanche material at the
base of the slope was removed by the ensuing flood. The catastrophic release of the stored
water and debris eroded a new channel below the dam.
Farther downstream, trees from the avalanche and the stream banks became jammed in the
channel along the south side of the alluvial fan. This diverted the debris-laden water
northward away from the sewage treatment plant. Residential and commercial property
was damaged, power lines were severed, and Spruce Creek Bridge was washed out.
Seward Flood Hazards Mitigation Plan
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Figure 4. Lowell Point - Spruce Creek Area
SEWARD CITY LIMITS
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Seward Flood Hazards Mitigation Plan
LOWELL
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In September 1982, a flood caused severe scour, lateral erosion and damage to the main
sewer line buried across the fan-delta. The 1989 flood damaged the sewer lagoon access road
and bridge abuhnent. During the September 1995 event rain water filled the sewer lagoon,
and the sewer pipe was exposed at the Spruce Creek crossing.
Past Mitigation Efforts
After the 1986 flood, the Soil Conservation Service (SCS) built a 1300 foot riprap revehnent
on the south bank of the channel upstream of the Spruce Creek Bridge. The revetment
trains the water flow under the bridge opening, and protects most of the development on
the fan. It has performed well since construction.
Mitigation Needs
The single most cost effective mitigation measure identified for Spruce Creek is to conduct
annual channel cleaning to keep the channel directed under the bridge and to ensure a
debris clear channel to the bay.
*Lowell Creek
The original townsite and older parts of Seward are built on the Lowell Creek alluvial fan
at the mouth of Lowell Canyon. The fan is 1.2 miles N-S and 0.5 miles E-W.
Flooding History
Following repeated flooding, damaging erosion and gravel depositior. within the townsite,
a diversion levee and a 2,OOO-foot long, 10-foot diameter tunnel were authorized by Congress
in 1937, and completed by the Corps of Engineers in 1940. The project diverted Lowell Creek
into Resurrection Bay at the southern edge of the City. Subsequently, debris-laden floods
through the tunnel have repetitively deposited large quantities of sediment over the Lowell
Point Bridge -- in August 1966, September 1967, October 1969, September 1976, September
1982, October 1986, August 1989 and again in September 1995. The 1982 event caused a large
volume of the protecting railing within the tunnel to be loosened and discharged from the
outlet.
During an August 1966 flood, high-water marks were 2 feet below the crest of the upstream
end of the Lowell Creek diversion levee, which angles across the stream; in October 1986 the
water came within 0.7 feet of the crest at this point. During the night of October 10-11,
debris from small landslides above the tunnel entrance, at the downstream end of the levee,
temporarily obstructed the entrance. Blockages of the tunnel entrance or breaching of the
Seward Flood Hazards Mitigation Plan
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levee dam would have caused flooding, erosion, and deposition through the City of Seward
downstream from the canyon mouth.
The flood of September 1995 produced a major event throughout the Lowell Creek drainage.
Multiple mud and rock slides covered the culvert bridge near the city limits. The ensuing
flood waters caused gravel filling at the north end of the Wards Cove Packing Dock
(formerly, Anderson Dock). The Lowell Point Road Bridge at the tunnel outfall received
severe pressure due to rushing water. The north approach was removed to relieve the
pressure. The bridge was covered with water and gravel, but only superficially damaged.
Resurrection Bay, in front of the tunnel outfall, was filled with gravel, and Railway Avenue
flooded back to 3rd Avenue. Sewer pump station #3 was threatened.
Past Mitigation Efforts
The tunnel received repairs in the winter of 1983-84, along with the cunstruction of a low-
flow diversion pipe down Lowell Canyon Road and Jefferson Street to the bay. This allows
for diversion of water during winter inspection and repairs.
In 1990 the Lowell Point Bridge was reconstructed further out from the outfall, raised to
a higher grade and supported by deeper piling. After the 1986 flood, the vault for sewer
pump station #3 on Railway Avenue near the Lowell Creek tunnel outfall area was
enclosed. The tunnel received emergency repairs in 1988 and 1990. However, it appears to
be deteriorating faster than it can be repaired.
Mitigation Alternatives
The existing structure continues to deteriorate despite maintenance efforts. Blockages of the
tunnel due to liner failure, debris or landslides could cause flood flow to go over the
spillway. There is no outfall channel, and the spillway is directly above the center of
Seward's most populated area including a senior citizen housing project. An overponding
flood could cause catastrophic damage and loss of life.
In September 1992, the Alaska District Corps of Engineers completed a reconnaissance-level
study of the possibility of modifying or replacing the Lowell Creek tunnel. The report
estimated that if the tunnel continues to receive only minor repairs, it will likely fail by 2015.
H concluded that feasible alternatives exist, and that there is a Federal interest in further
studies.
Nine alternatives for controlling Lowell Creek flooding were described in the report. Two
were recommended for further investigation: (1) rehabilitate the existing tunnel and add an
emergency spillway and slit dam; and (2) add a second IO-foot tunnel to the rehabilitated
Seward Flood Hazards Mitigation Plan
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LOWELL. CREEK
existing tunnel. The cost to benefit ratios of both alternatives exceeds general practice for
projects of this kind.
Lowell Creek outfall and tunnel analysis
Lowell Creek is the most urgent mitigation need in Seward. The Corps of Engineers 1992
reconnaissance study paints a bleak picture of the diversion dam and tunnel. The tunnel
is now 55 years old and deteriorating faster than it can be repaired. It is estimated that the
value (in 1996 dollars) of property that would be lost as a result of tunnel failure would be
nearly $17 million dollars. There is also probability for loss of life should the city center
suddenly be inundated by a catastrophic flood of the magnitude estimated should the
existing structure fail, or plug.
The Corps study indicates that it will cost over 22 million dollars to implement its
recommendations for Lowell Creek. Clearly the City does not have this kind of money, and
the Corps has stated that the cost to benefit ratio would preclude their recommending
spending Corps funds. These are major projects which will require help from the State of
Alaska, the United States Congress and money from State and Federal agency grant and
other programs. The City should begin immediately to seek funding for Lowell Creek. A
pragmatic view of project funding indicates that a great deal of time and work will be
required by the City to secure the necessary dollars.
Mitigation of the tunnel outfall and the tunnel should be considered in three stages:
(1) The existing tunnel should be refurbished.
(2) The tunnel outfall should be extended as a flume over the road and bridge into
deeper water. This will protect the existing bridge, and will help solve the problem of debris
fill and wash out of bridge approaches during major flooding events, and
(3) A second tunnel should be constructed.
These alternatives will not pass the probable maximum flood (PMF). They will, however,
provide a margin of safety to life and property within the limits of proper preparedness.
While working toward these major projects, smaller projects to lessen the risk should be
developed including considering limiting future development downstream along Jefferson
Street. The Lowell Creek stream gauge has been removed because of the dynamics of the
creek. In a cooperation with USGS and the National Weather Service, explore ways to
improve flood warning through water level alarms.
Seward Flood Hazards Mitigation Plan
14
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*Rudolph (Scheffler) Creek
Rudolph (Scheffler) Creek drains a high-altitude, glaciated basin between Mt. Marathon and
Phoenix Peak, flows along Barwell Street and Phoenix Road into the "Lagoon" and exits to
the Bay by way of the Fish Ditch. it is a small babbling brook during normal times, but
during flooding events its impact on the Lagoon can threaten homes as far away as 2nd
Avenue and Van Buren Street. It is too small a drainage area to be addressed by the Corps
of Engineers.
Flooding History
During the October 1986 storm, water from the Rudolph (Scheffler) Creek washed out
culverts and road beds along Barwell and Phoenix and deposited coarse sediment in the
north end of the Lagoon. Rapid runoff from this creek and several other small mountain
streams combined to cause the Lagoon to rise, which in turn caused extensive flooding along
2nd, 3rd and 4th Avenues. In the small boat harbor area, Lagoon overflow eroded the
saturated fill and deposited the sediment in the small boat harbor.
During the September 1995 stonn, the Lagoon again filled, overflowing Dairy Hill Lane and
flooding the vacant land at the south end of the Lagoon. This, combined with runoff from
First and Second Lakes, flooded the 2nd Ave. and Van Buren St. intersection. The south end
of Chiswell Street was superficially damaged by surface runoff water which then washed
out and closed BarwelL The latter two are gravel streets.
Within the Bayview and Gateway areas, home owners have slowed or blocked small
waterways to create ponds, waterfalls and meandering brooks on their property. While
these measures are deemed aesthetic by the property owner, they disrupt the natural
drainage patterns causing serious problems not only for the property owner, but for those
down stream as well. These waters eventually flooded Chiswell Street before draining into
Rudolph (Scheffler) Creek at Barwell Street.
Past Mitigation Efforts
After the 1986 stonn, riprap was placed along the creek bank where it curves at the Barwell -
Phoenix intersection.
Mitigation Needs
Consider larger or additional culverts to allow high water from the Lagoon across 3rd and
4th Avenues to flow through the Fish Ditch to the bay.
Seward Flood Hazards Mitigation Plan
IS
Figure 7. Scheffler (Rudolf) Creek and Lagoon Area
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Seward Flood Hazards Mitigation Plan
16
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Lower and annually clean the Fish Ditch channel to assure easy runoff during flooding.
Consider paving the area east of 4th Avenue between the small boat harbor and Harbor
Lights Condominiums. With adequate sloping, it would allow Lagoon flood waters that
overtop 3rd and 4th A venues to flow to the beach without serious land erosion.
*lM!lanese) Creek
Jap(anese) Creek originates in a high, glaciated basin that drains through canyon walls that
have been greatly over-steepened by glacial erosion. At the canyon mouth, a broad fan 1.5
miles long and 1 mile wide extends to the valley alluvium of Resurrection River. This creek
has flooded more often, and shown the potential for flooding greater areas, than any other
stream within the city.
Flooding History
As in other alpine basins in the Seward area, retreating glaciers have left lateral moraines
perched on steep slopes in the upper basin of Jap(anese) Creek. A large landslide 0.1 miles
above the canyon mouth was reactivated by the intense rainfall during the 1986 storm and
deposited rock and boulders as large as 6 feet in diameter in the stream channel. When the
debris dam failed, the flood washed out a man made earthen levee along the southeast
stream bank at the apex of the fan. The creek then threatened to move into abandoned
channels to the south and east into Forest Acres. Similar flooding and erosion occurred at
this site in August 1966. The flood-fighting efforts of bulldozer operators, working
continuously through the night of October 10-11, 1986, contained this creek within this most
recent flathead trench.
Debris-laden floods in August 1966, October 1969, September 1976, September 1982, and
again in October 1986, document the frequent recurrence of stream damming and surge-
release flooding of sufficient volume to be transported past the canyon mouth to affect the
lower portion of the alluvial fan. The flathead trench conveyed sediment-laden water to the
lower portion of the fan where the active stream channel widens, the slope decreases, and
rapid deposition occurs. In October 1986, the flood flow migrated laterally, inundating and
eroding roads west of Forest Acres Subdivision.
During the August 1989 and September 1995 storms, the creek tried to change course
through the western edge of Forest Acres Subdivision. Workers kept it within its channel.
Creek waters join Resurrection River to flood southerly along the highway embankment
into the undeveloped Forest Acres and Fort Raymond areas.
Seward Flood Hazards Mitigation Plan
17
Figure 8. Jap(anese) Creek - Resurrection River Areas
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Seward Flood Hazards Mitigation Plan
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Past Mitigation Efforts
During the 1986 flood, the right descending channel bank of ]ap(anese) Creek, starting at the
apex of the fan, began to erode. After the flood, the Soil Conservation Service (SCS)
constructed a riprap levee along the channel. The levee is 1,150 feet long with an average
height of 13 feet. This levee protects the bank from further erosion, and helps confine the
channel to the left margin of the fan.
Mitigation Alternatives
Two major mitigation measures should be considered that will significantly alleviate
flooding from ]ap(anese) Creek. They are estimated to cost approximately 2 million dollars,
but when broken down into project phases, the costs for these projects are sufficiently less
than the stages of Lowell Creek mitigation. Each of the phases will cost approximately 500
thousand dollars.
Phase (1). Development of a North Forest Acres Road and levee from the Seward
Highway to Dimond Blvd. Since the creek mingles with the Resurrection River upstream
from the Seward Highway, this project may also provide protection from the river.
Phase (2). Continued construction of North Forest Acres Road from Dimond Blvd. to
the northwest comer of Forest Acres subdivision.
Phase (3). Extending the levee, constructed by the Soil Conservation Service after the
1986 event, 2,400 feet to the northwest comer of Forest Acres Subdivision.
A funding source that should be sought immediately is the Hazard Mitigation Grant
Program funded by the Federal Emergency Management Agency and administered by the
State of Alaska Division of Emergency Services (ADES). The City is eligible to receive money
from this grant program based on the Presidential declaration of emergency after the
September 1995 flood. A total of approximately one million dollars is available to the
government agencies meeting the requirements of this program. Appl \' for a grant of up to
500 thousand dollars for phase one upon approval of the plan by the City Planning and
Zoning Commission, City Council and State of Alaska.
Other mitigation measures include continued levee maintenance, channel maintenance
dredging, and additional or larger culverts where needed.
Seward Flood Hazards Mitigation Plan
19
*Resurrection River Basin
Resurrection River flows in a southeasterly direction along the city limits into the head of
Resurrection Bay. Although numerous named and unnamed tributaries contribute flow to
the main channel of the river, }ap(anese) Creek is the main contributor within the City.
Flooding History
Resurrection River was a major source of flood water backing up behind the Seward
Highway road bed into the lower Forest Acres and Fort Raymond Air Force Recreation
Camp areas in both 1986 and 1995. In 1995, intermingled waters from }ap(anese) Creek and
Resurrection River overtopped the Seward Highway, breached the Alaska Railroad track
bed to ultimately erode areas of the Leirer Industrial Park, the railroad yard, Port Avenue
and the harbor area uplands. As a result, a large sediment mass was deposited in the
northeast comer of the Seward Small Boat Harbor basin. The Alascom trans-Pacific fiber
optic cable and digital switching station were threatened, as were the Shoreside Petroleum
fuel tanks and a new A VTEC classroom building. The fisheries meal plant building was
undermined and partially collapsed.
A major shift in the river channel in 1995 severely threatened the Seward Airport. Flood
water overtopped the runway and eroded the taxiway between the two runways. A
concentrated amount of rock deposited along the east runway during the flood prevented
destruction of the airport by the river.
An earlier partial shift in the river channel had deposited a large volume of sediment in
the Alaska Railroad Dock's east basin. This area was dredged in the spring of 1995. The fall
storm caused the entire river volume to divert to the new channel. Much of the earlier
dredging was negated by the sediment deposited by the flooding.
Mitigation Efforts
The Kenai Peninsula Borough constructed a 1,300 foot long rock levee in the early 1980's to
protect the Seward Landfill. The levee was extended an additional 1,200 feet after the 1986
flood.
Immediately following the 1995 event, the Alaska Department of Transportation and Public
Facilities was able to obtain permits to deepen the old channel to rel'pen it to water flow.
This effort dramatically reduced the volume of water threatening the east side of the airport.
Seward Flood Hazards Mitigation Plan
20
-
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Mitigation Alternatives
All the facilities discussed are of great importance to the community, however, most are
covered by mitigation plans being prepared by the Kenai Peninsula Borough, the Alaska
Railroad and the Alaska Deparhnent of Transportation and Public Facilities. It is anticipated
that the following proposed mitigation projects are or will possibly be addressed by other
plans.
a) Consider extending the Kenai Peninsula Borough levee :t7,2o.o. feet along
Resurrection River to a point between the Middle and Jap(anese) Creek Bridges on the
Seward Highway. This, in combination with the North Forest Acres Roadllevee would
protect the solid waste transfer facility, Forest Acres, and Fort Raymond areas as well as the
highway, railroad yard and small boat harbor areas.
b) The Alaska Railroad has begun permitting and design work to construct a groin
to protect the dock's east basin from further sediment deposition. The Railroad has also
addressed the need to modify its trestles to provide longer clear spans which will allow for
greater water flow and minimize debris loading.
c) Alaska Department of Transportation personnel are in the design phase for the
Mile 0.-36 Seward Highway reconstruction project. This project is expected to address
Resurrection River bridges, their spans and adequate drainage to allow water through the
roadbed to the bay.
d) Channel dredging at the mouth of the river would promote flushing of the
sediment. This would in turn reduce the upstream sediment buildup, which encourages the
movement of the river from high to lower areas, and lessen flooding potential upstream.
The following projects related to mitigating Resurrection River flood waters are of city
interest.
a) Although there is a storm drain in Port Avenue that ties into an old 6 inch sewer
outfall on the east side of the ARR Dock, it is inadequate to handle flood conditions. This
lack of capacity contributed to 1995 flood waters to break through Port Avenue into the small
boat harbor basin. Adequate drainage through the industrial areas to the bay should be
considered.
b) A sheet pile facing around the northeast perimeter of the small boat harbor basin
would prevent future sediment deposition in the basin. The cost at $2Q/SF is estimated to be
between $130.,0.00 and $150.,0.0.0. depending upon the piling configuration.
Seward Flood Hazards Mitigation Plan
22
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*Sawmill Creek
The headwaters of Sawmill Creek drain several high-altitude glaciated basins with steep
alluvial fans at the mountain front. The creek enters the city limits northeast of Nash Road
and flows southwest under the Sawmill Creek Bridge. Below the bridge, the stream traverses
the valley alluvium in low-banked, braided channels of high gradient. Only that portion of
the creek drainage below Nash Road is within the City.
Flooding History
In the October 1986 storm, many log and debris jams along the stream channel caused
considerable lateral bank erosion and diversion of flood waters into abandoned channels.
These channels then conveyed water throughout the flood plain. During the flood, the
water surface rose to 1.0 feet above the lowest point of the Sawmill Creek Bridge
superstructure, and 17 feet of the south road abutment washed out. The water combined
with runoff from two small unnamed mountain drainages to flow over Nash Road at mile
2.4.
Local flooding from small drainages and erosion along gravel roads occurred in the
Nashwoods residential area. Floodwaters concentrated in the gravel roads oriented parallel
to overflow channels, thereby reducing damage to structures located on the flood plain.
During the 1995 event, flooding occurred downstream from the bridge and threatened
electric power poles on the private industrial property at the head of Resurrection Bay.
Past Mitigation
After the 1986 flood, the state constructed a new bridge over Sawmill Creek. The channel
was widened and deepened, and the banks were riprapped. This greatly reduced the 1995
flood damage in this area.
Mitigation Needs
Annual cleaning should be conducted to maintain adequate channel depth to promote
flushing.
*Fourth of Julv Creek
Fourth of July Creek is located on an alluvial fan on the eastern shore of Resurrection Bay
opposite the City of Seward. It was formed by two glacial-meltwater streams--Fourth of July
Creek and Godwin Creek. The streams are deeply incised in bedrock above the apex of the
Seward Flood Hazards Mitigation Plan
23
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fan. Prior to its relocation and containment by levees constructed as a part of the
development of the Seward Marine Industrial Center (SMIC), the creek flowed 3.4 miles
from the canyon mouth along braided distributary channels to the broad 1.26-square-mile
fan. There it meandered, and discharged along the 1.5-mile-long base of the fan into
Resurrection Bay.
Flooding History
In October 1986, landslides, slumping and other slope failures in the steep-walled canyon
on Godwin Creek formed at least five dams across the channel which resulted in short-term
storage of water and rock debris. Subsequent breaching of the dams by floodwater inflow
mobilized a surge-release, debris-laden flood through the canyon and below the canyon
mouth. Aerial photographs show deposits from such floods scattered over the bedrock in
the canyon. The surge release produced a flood whose maximum unit discharge was
substantially greater than any previously known flood in Alaska.
Boulder fronts and terrace-like boulder berms extending across the flood channels with the
coarsest material, at or near the surface, were left by the flood surge. These nearly flat-
topped berms extended continuously on both sides of the channel downstream from the fan
apex near the canyon mouth.
The berm surface was as much as 10 to 15 feet above the present channel, although it was
below the high-water marks on the valley walls. Boulders were deposited to a depth as great
as 10 feet around the base of mature spruce trees. The trees were scarred 4 to 6 feet above
the boulder terraces, which indicated that a debris-laden flood rather than a debris flow
occurred below the canyon. Evidence of mass movement debris flows below the canyon may
have been destroyed or modified by the subsequent debris-laden flood. Trees more than 100
years old growing along the vegetated glacial rock debris deposited over bedrock were
scarred and ripped from bedrock crevasses to a height of 15 feet above the bed of the main
channel.
The flood of October 1986 eroded new channels across the upper reaches of the Fourth of
July Creek alluvial fan, and it inundated and deposited great quantities of coarse gravel,
cobbles, and boulders over the entire surface of the fan upstream from the levees. Although
the levees were severely eroded and overtopped in places, they did confine most of the flood
flow to the levee channel. High-water marks surveyed along the eroded upstream face of
the 650-foot-Iong diversion levee were 3.1 feet below the levee crest.
Past Mitigation Efforts
After the 1986 flood, the Corps conducted two flood control studies of Fourth of July Creek.
Seward Rood Hazards Mitigation Plan
25
The first report (U5ACE Alaska Dishict March 1991) concluded that an economically feasible
project with a Federal interest existed. The recommended alternative modified an existing
diversion and flood control levee constructed in 1982.
High flow conditions had caused damage to the existing flood control structures. The
existing levee diverts the creek away from the prison facility. Debris jams during past
events had directed high-velocity flow onto the lower portions of the levee and the levee toe.
The report concluded that if no action was taken the prison and industrial area would be
subject to damage from 50-year events or greater.
During the fall of 1991, the City used locally available funds to modify the existing levees.
These modifications included a launching apron built along the north diversion levee at the
southern end and three new spur dikes along the main levee. After this modification, the
Corps revised its flood control study for Fourth of July Creek, concluding that because of the
levee changes, Federal participation could no longer be justified. The city does have a Corps
permit for annual channel maintenance work.
Mitigation needs
Measures should be taken to dredge the mouth of the creek to promote flushing and create
a direct channel to the bay. At present, rubble in the creek is almost level with the banks.
The levee on the east side of the prison is in need of repair and should be raised 8 feet. Two
or three additional spur dikes are needed to complete the toe protection on the upstream
end of the levee.
Seward Flood Hazards Mitigation Plan
26
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OTHER ISSUES AND MITIGATION
RECOMMENDA TIONS
The City subdivision code should be amended to include flood hazard mitigation measures
and provisions for City authority to control drainage of surface water, including creeks and
brooks on private land.
Numerous slide areas along the east face of Bear Mountain affect Lowell Point Road with
snow, rocks and mud. Although it may not be cost effective, one mitigation measure would
be to construct shedding structures in slide areas along the road. Slide material would add
rock armor along the shoreline beside the road.
In cooperation with the Kenai Peninsula Borough, USGS, the National Weather Service and
the Alaska Department of Transportation and Public Facilities, explore ways to improve
flood forecasting through the use of stream gauges, weather stations, doppler radar and
water level alarms, as well as the timely dissemination of information. Such systems
normally involve not only initial purchase and installation but ongoing operations and
maintenance funding.
To underscore the importance of many of the projects identified in this plan, the City
should annually budget a specific amount of money to a flood mitigation fund. In this way
money that can't be appropriated immediately can be built up over time.
Seward Flood Hazards Mitigation Plan
27
CONCLUSION
Many of the mitigation measures taken after the 1986 flood have had a positive effect in
mitigating overall flood damage in Seward. Some, such as the Soil Conservation Service
riprap revetment at Spruce Creek, effectively mitigitated a large problem at Lowell Point.
There is no "one fix" measure which can be taken to solve the immense flooding problems
within the City of Seward. As has been shown by documentation of the City's flooding
history, the process by which alluvial fans are built precludes delineating an accurate flood
zone along streams which can shift suddenly during heavy rains exposing the entire fan to
flooding.
Both time and budget constraints preclude acquisition of detailed enh>ineering and field data
for conclusive development of project costs and design. The measures set out in this plan
are potential alternatives to alleviate flood threats to life and property.
Many things must be taken into account before solutions can be projected. Infrastructure
projects up stream affect infrastructure down stream. Building a road, dike or levee may
help one area, but could create problems in other areas. Therefore, all mitigation projects
will require detailed hydrologic and engineering analysis before implementation.
Many of the mitigation measures involve annual expenditures to remove debris or otherwise
maintain waterway channels to lessen future flooding. Generally these can be carried out
by the City with little help from outside sources.
It should be noted that agreements with other agencies providing mitigation money to the
City in the past have included wording to the effect that money would be budgeted for
operation and maintenance of these projects (Soil Conservation Service Agreement,
November 1986, Operation and Maintenance Agreement).
In addition, it will be necessary to explore all possible funding sources or cost sharing
partnerships including the State Legislature and the United States Congress to fund
mitigation projects for the Lowell Creek outfall and tunnel and Japanese Creek levees.
Seward Flood Hazards Mitigation Plan
28
t~Hve Summ,'Y of H'wd ., Sewo<d :::~::U:'~~:O<b'" Re,uoc,cHon Rive, F.n-DeI',
Sedimentation, FEMA Region 1() Hazard Mitigation Technical Assistance Team. DR-1072-Ak,
Oct 1995
Flood Hazard Mitigation Plan Milepost 0.0 to Milepost 355.0, Alaska Railroad Corporation, 1986
Flood of October 1986 at Seward Alaska, USGS Water Resources Investigations Report 87-4278,
Jones, Stanley H. and Chester Zenone, USGS, 1988
Hazard Mitigation Plan for the Seward Area (Draft), Kenai Peninsula Borough Planning
Deparhnent, Sep 1987
Interagency Hazard Mitigation Report FEMA-782-DR-AK Alaska, Federal Emergency Management
Agency, Nov 1986
Japanese and Spruce Creek Project Agreement, United States Department of Agriculture Soil
Conservation Service, Nov 1986
anese and S ruce Creek Streambank Protection 0 eration and Maintenance A
States Deparbnent of Agriculture Soil Conservation Service, Nov 1986
Lowell Creek Flood Control Works, Seward, Alaska, Operation and Maintenance Manual, U.S.
Army Corps of Engineers, Alaska District, Jun 1969
Lowell Creek Dam, AK 00060 Seward Alaska, Phase I Inspection Report~ational Dam Safety
Program, U.s. Army Corps of Engineers Alaska District for State of Alaska and City of
Seward, Nov 1978
Lowell Creek Tunnel, Seward, Alaska, Study of Alternatives for Reconstruction, CH2M Hill for City
of Seward, Apr 1983
Lowell Creek Tunnel Repair Project Report, Acres/Hanscomb, J.V., Aug 1984.
Lowell Creek Flood Control, Seward, Alaska Reconnaissance Report Modifications to Completed
Project, U.S. Army Corps of Engineers Alaska District, Nov 1988
Lowell Creek Seward, Alaska Flood Damage Reduction Interim Reconnaissance Report, U.S. Army
, Co,!" of Enginee~ AI"k. D"'ricl, J.n 1991
Seward Flood Hazards Mitigation Plan
29
Lowell Creek Seward, Alaska Flood Damage Reduction Revised Reconnaissance Report, Us. Army
Corps of Engineers Alaska District, Aug 1992
Seward Area Rivers Flood Damage Prevention Interim Reconnaissance Report, U.s. Army Corps
of Engineers Alaska District, Feb 1994
Seward Flood of September 18-24, 1995 and Channel Reconstruction of the Resurrection River,
Barber, Skip Alaska Deparhnent of Transportation and Public Facilities Central Region, Oct
1995
Seward Flood Hazards Mitigation Plan
30
,
,
,
Seward Flood Hazards Mitigation Plan
APPENDIX
31
Land Use Flan
Land Use opportunities and Constraints
\
Seward is blessed with a diversity of water
features, beaches, and forested mountainsides,
birds and marine life. This natural heritage is not
only a magnilicent scenic and recreational setting
for the town, it is also a sensitive environment
which imposes severe constraints on development.
The Comprehensive Plan establishes the following
guidelines for preserving this heritage, by
managing or restricting development in sensitive
areas.
6. Protect citizens from natural
hazards through land use poUcies and
regulations. The City shall: .
a. Restrict development in areas of high seismic
risk, steep slopes, and avalanche areas, as
identified in Fig. 2. Incorporate by reference in
the Comprehensive plan, U.S. Geological
Survey Paper 542-E, prepared after the 1964
earthquake. This report remains the best source
of information on guidelines for the prevention
of damage in the event of another earthquake.
b. Restrict development of habitable buildings in
areas identified in a., as well as in areas of
river flooding and tidal inundation, as shown
in Fig. 2.
c. Resolve to participate in the National Flood
Insurance prOgram of the Federal Emergency
Management Agency, stipulating that habitable
floor areas shall be built above the designated
100 year flood level, and implementing that
requirement through the City's building permit
program and the Borough subdivision
ordinance.
d. Restrict development of any structures within
that portion of the floodplain identified as the
Floodway, necessary to pass flood flowS
without a significant increase in flood height
(Fig. 2).
e. Require applicants for building permits for
properties in or adjacent to the floodplain to
submit a topographic survey map documenting
the limit of lOO-year floodplain and finish
elevations of aU structures.
f. Advise developers of U.S. Army Corps of
Engineers permit requirements for 1.) !in along
coastlines beloW 13.8 feet elevation, 2.)
structures along coastlines below 9.5 feet
elevation, 3.) any development beloW ordinary
high water in streams, and 4.) any
development in wetlands.
g. Request that the Corps of Engineers create
maps which identify and classify wetlands on
the basis of resource value. Enact an
ordinance which establishes a general permit
procedure _ consistent with Sec. 404 of the
Clean Water Act - for regulating development
in or near various classi!ied wetlands.
h. Participate in development of the Borough
Coastal Management Plan to integrate planning
of the Resurrection River flood plain, which is
bisected hy the Seward City limits. Update the
ComprehensiVe Plan to insure consistency with
the Borough Coastal Management plan, when
it is completed and approved by the State.
i. Extend roads and utilities to areas of future
development which have the least restrictions;
and conversely, avoid public funding for
improvements which may encourage develoP-
ment of hazardous areas.
j. Develop the most feasible areas first, reserving
areas with possible building limitations as a
study reserve (Fig. 3).
7. Maintain good water quality for
residents and fisheries. The City shall:
a. Restrict development within the Lowell Creek
watershed to protect the city's potable water
source.
b. Establish development setbacks from salmon
rearing habitats and spawning streams as
Identifled by the Alaska ~ent of Fish and
Game In Fig, 2, in response to that agency's
Title 16 permit requirements, by amendment to
the zoning ordinance (perhaps by creation of an
overlay zone),
.....,..., ,-
..lAta):> <.0 t-'l prte-HE'AlSI\I € PLoAN
----'"
c. Review water quality tests being performed by
the Alaska Department of Environmental
conservatiOn in Resurrection River, adjacent to
the Borough landfill, as an expression of public
policY concern over maintenance of water
quality in Resurrection River.
d, Protect from development, the identified
feeding, and nesting areas for shorebirds and
hunting areas for raptors in wetlands within
the designated industrial area around the
airport (Fig. 2.)
e. Pass a resolution informing the Borough of the
City's concern about the potential for
haphazard development outside the City
Limits, particularly in the Resurrection River
floodplain.
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Harbor Land Use
1. Conflicts Now Exist Between Recreational Boats and Commercial Boats Using the Small Boat Harbo,
Slips Slde-By-Side
a. Continue efforts to designate harbor slips for use by recreational boats and slips for commercial boats so lhat
both can use the harbor and co-exist without conflict
2. Commercial Development Is Blocking the Access and Views of the Boats Within the Small Boat Harbor
a. Encourage development of commercial facilities to those areas west of Founh Avenue
b. Encourage private development/redevelopment east of Fourth Avenue to one-story structurcs.
Resource Mana2ement
1. Seward Must Protect Its Natural Environment and Ensure the Safe Development of the Community
Consistent With the Natural Resources and Natural Hazards of the Community
a. Continue to restrict development in areas of high seismic risk, steep slo~ and avalanche areas consistent with
the U.S. Geological Survey Paper S42-E, prepared after the 1964 earthquake
b. Continue to restrict development of habitable buildings ill areas identified in the above noted areas as well
as in areas of river flooding and tidal inundation
c. Continue panicipation ill the National F100cllDsurance Program
d Seek methods of ensuring the protection of the Jeffenon Strect/LoWell Canyon Road area from flood potential
resulting from overflow of the Lowell Creek spillway
e. Require applicants for building permits for properties ill or adjacent to the floodplain to submit topographical
survey maps documenting the limit of the 100 year floodplain and finish elevations of all structures
L Advise developers of the U.S. Army Corps of Engineers permit requirements for: fill along coas~lines be10w
13.8 foot elevation; structures along coastlines below 9.5 foot elevation; any development below ordinary high
water in streams; and any development ill wetlands
g. Develop a system, in conjunction with the Corps of Engineers, which establishes a permit procedure for
regulating development in or near various classified wetlands
h. Cooperate with the Borough in all coastal management planning
i. Continue to express concern to the Borough concerning development within the Resurrection River Salmon
Creek floodplain outside the City limits
'Seward DO Compn:b_ t'\aa.
31