HomeMy WebLinkAbout#01 - Spring FloodingSTAFF REPORT
DATE: February 11, 2020
DISCUSSION
AGENDA ITEM: Flooding
TO: Mayor and Council
SUBMITTED BY: Kristina Handt, City Administrator
BACKGROUND:
At a previous work session council asked to discuss flooding concerns ahead of the spring thaw.
ISSUE BEFORE COUNCIL:
What is the City’s role in addressing flooding concerns?
PROPOSAL DETAILS/ANALYSIS:
City staff has had communications with the watershed staff and staff from Washington County regarding
potential flooding issues in Lake Elmo. After the 2019 Spring floods, the watershed district provided maps
of areas that had complained about flooding. Those maps are included in your packet. I met with John
Hanson in July to review these parcel and discuss any possible actions the city could take in the future. In
most cases due to the topography of private property, it would be up to the property owner to construct a
berm on their property if they wanted to prevent flooding. There were some culverts that we knew had
gotten plugged such as on 50th St and Jamaca last spring which public works will prioritize this year to
minimize backups. Due to liability concerns, the city’s position in the past has been that we won’t go onto
private property to do anything in response to flooding. The city will focus on its public infrastructure-
roadways, culverts, etc. Similarly, Washington County focuses on their public infrastructure-county roads.
The county has also communicated that they can provide sand and sand bags as needed to city, not private
property owners. We have already ordered 2,000 sand bags and the sand will be delivered if/when needed.
We continue to get regular updates from Washington County regarding the flooding situation. Included in
your packet is the most recent update from the National Weather Service.
Lastly, we have included information about the National Flood Insurance Program in the FRESH on a
regular basis as well as in the Winter issue of the Source. Folks need to be aware that the insurance doesn’t
go into effect until 30 days after purchase so they should plan ahead.
FISCAL IMPACT:
For cities and townships requesting assistance from Washington County with sand/bags procurement, the
following is the county rate for sand and sandbag requests:
On average, 70 sandbags (14 X 36) will use one ton of sand.
Item Amount Cost
One delivery of sand and bags 10 Tons of sand and 700 sand bags $225
One delivery of sand only One deliver of sand only $120
One deliver of sand bags only One deliver of bags only $105
The costs listed above do not cover county staff time for loading product or delivery, fuel, etc. Public Works
is charging for their costs of the product only.
If other items are needed, for example a jet to clear culverts, staff would review options of contracting for
that at the time it is needed. If we are unable to find one, Washington County may be able to help with the
procurement.
ATTACHMENT:
• 2019 Flood Areas
• National Weather Service Flood Outlook
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What does this mean?
Before we even look at snowpack, the soil and rivers are primed for high runoff .
A low snowpack would help reduce the flood threat, but a normal or high snowpack would
increase the risk of major spring flooding. Much like last year, the type of melt we get will be a
major factor. Recall that
we had a nearly ideal melt in spring 2019
(mild days with cold nights for recovery, and a three-week period of no rain/snow in March).
Even a “normal” melt season would result in significant spring flooding this time around.
Situation Report
Friday, January 24, 2020 11:48 AM
National Weather Service
City, State
Early Spring Flood Outlook –Elevated Threat
•Current conditions suggest spring flooding will be more likely than in a typical
year, throughout the upper midwest. However, significant flooding is not certain.
•Major contributing factors to flood potential will be determined over the winter
months.
Soils are Wet
All of the upper Midwest received well above normal
rain again this fall,mostly 150 to 200 percent of
normal.This continued to supply soils with excess
moisture as we froze the upper portion of the soil.
Streamflow is High
Going into seasonal freeze-up,river levels
throughout the upper Midwest remained very high,
with many showing record levels for early winter.
What Do We Know So Far?
National Weather Service
Twin Cities / Chanhassen, MN
nws.twincites@noaa.gov
mobile.weather.gov
weather.gov/mpx
Friday, January 24, 2020
National Weather Service
Twin Cities / Chanhassen, MN
Friday, January 24, 2020
Winter 2019: Precipitation Outlook
Outlooks continue to favor near to above normal
precipitation for the winter months. The indicators are
fairly weak in the global pattern this winter (no strong El
Niño or La Niña), so confidence is not particularly high
this year. Temperatures will be fairly mild into early
February, then potentially below normal the rest of the
month.
Keep in mind…even a normal amount of precipitation
this winter season would bring an elevated risk for
flooding this upcoming spring.
Potential Flooding Impacts For Winter/Spring
•Widespread flooding affecting infrastructure in
Spring 2020
•Including lakes, lowlands, agriculture,
overland flooding.
•Elevated risk for ice jams
The National Weather Service urges those who would be affected by flooding to
Prepare Now and stay tuned to updates as we move through the winter into early spring.
nws.twincites@noaa.gov
mobile.weather.gov
weather.gov/mpx
The updated Winter Outlook for Jan-Mar 2020 indicates
slightly higher than normal chances for above normal
precipitation.
2020 Probabilistic Spring
Flood Outlook Dates:
February 13, 2020
February 27, 2020
March 12, 2020
Spring Flood Threat Checklist (as of mid January)
Threat Impact to Potential Spring
Flooding
Link to Image
High river levels Increased Threat USGS WaterWatch
High soil moisture Increased Threat CPC Soil Moisture
Winter Precipitation To Be Determined Winter Outlook
Snowpack/Liquid Equivalent To Be Determined Snow Analysis
Rate of Snowmelt To Be Determined 24,48, & 72 hr Snowmelt
Frost Depth*So far, decreased threat Frost Depth Map
Spring Precipitation To Be Determined Precip Forecast (in season)
Next Update Planned for mid February
* Frost depth is fairly shallow so far this winter due to mild temperatures and early snow “blanket”.
National Weather Service
Twin Cities / Chanhassen, MN
Friday, January 24, 2020
nws.twincites@noaa.gov
mobile.weather.gov
weather.gov/mpx
How to Read the Long Range Flood Risk Graphics –
at https://water.weather.gov/ahps2/long_range.php?wfo=mpx