Coastal flood impact assessments for Alaska communities
Presented by Richard Buzard Collaborators: Jacquelyn Overbeck, Jonathan Chriest, Karen Endres, and Edward Plumb THE PROBLEM
Storm surge flooding affects every coastal community in western Alaska.
The history of flooding in a community is difficult to follow How many storms have hit? How high have floods reached?
Knowing the flood history helps inform: Forecasters Mitigation planners WHERE CAN I FIND FLOOD INFORMATION?
Flood resources are scattered There is no consistent, full list of floods for each community So, we started putting together a list!
Source Description City of Golovin (2015) Local HMP Update City of Golovin (2008) Local HMP USACE (2017) Local Flood Report (online) Golovin USACE (2007) Local Erosion Report USACE (2000) Local Flood Report (print) Wise et al. (1981) State Storm Damage Report Chapman et al. (2009) Regional Storm Surge Model Many other sources Science, news, local reporting EXAMPLE: STORM HISTORY OF GOLOVIN
Hazard Mitigation Plan No single source is complete, and everything becomes Flood is mentioned had the most information dated, but together they make a long history of storms! Flood is not mentioned Flood occurred outside time of source Storm surge flood events (23 total) 03 10 01 11 08 09 05 28 25 02 05 08 19 05 29 30 13 12 12 22 11 ------SEP - OCT OCT OCT OCT NOV SEP - OCT OCT SEP NOV OCT SEP - JAN NOV NOV OCT NOV OCT DEC - OCT FEB AUG ------report
Source Description # of storms in given Percent time period total of Percent storms 1900 1913 1945 1946 1960 1974 1977 1992 2002 2003 2003 2004 2005 2008 2009 2011 2012 2013 2016 2016 2017 2019 2019 City of Golovin (2015) Local HMP Update 9 50% 39% 1 1 1 1 1 1 1 1 1 City of Golovin (2008) Local HMP 10 71% 43% 1 1 1 1 1 1 1 1 1 1 USACE (2017) Local Flood Report (online) 3 15% 13% 1 1 1 USACE (2007) Local Erosion Report 4 31% 17% 1 1 1 1 USACE (2000) Local Flood Report (print) 2 25% 9% 1 1 Wise et al. (1981) State Storm Damage Report 4 57% 17% 1 1 1 1 Chapman et al. (2009) Regional Storm Surge Model 3 38% 13% 1 1 1 Many other sources Science, news, local reporting 23 ? ? Top 10 Storm surge model But missed caught three big storms five others ESTIMATING STORM HEIGHTS (EXAMPLE: NOVEMBER 2013)
A series of four storms drove water into Norton Sound Standing water rose as high as Antone Street, but no significant overtopping occurred
Antone Street Golovin
standing water
Photo sent from Steve Ivanoff Figure by Emily Niebuhr, NOAA ESTIMATING STORM HEIGHTS (EXAMPLE: NOVEMBER 2013)
Feature Water on Antone Street Feature represents Highest water A series of four storms drove water into Water level type Still water Estimate of height (ft MHHW) 10.5 Norton Sound Elevation model error (ft) 0.7 Source data used uncertainty 1.0 Standing water rose as high as Antone Street, Mean and uncertainty (ft MHHW) 10.5 ± 1.2 but no significant overtopping occurred Estimate storm height Antone Street
Antone Street on Sept. 5, 2013 (m NAVD88) 5.2 5.1 5 4.9 standing 4.8 4.7 water 0 400 Feet 4.6 ± 0 100 Meters 0 20 40 60 80 100 120 140 160 180 Distance (m) SW to NE Use context clues Take storm observation to find location Measure elevation THOROUGH DOCUMENTATION
Report of Investigations with storm history, height, and estimation method Every storm! LIST OF STORMS
Vertical Elevation Rank Storm Uncertainty (ft MHHW) (ft) 1 1913-OCT-05 12 2 2 1974-NOV-10 11 3 3 2013-NOV-09 10.5 1.2 Great! 4 1992-OCT-05 10.0 0.9 5 1945-OCT-28 9.1 1.4 Not enough But what does it mean? 6 2011-NOV-08 9 2 information 7 2004-OCT-19 8.9 1.1 1900-SEP-12 8 2005-SEP-22 8.8 0.3 1946-OCT-25 9 2016-DEC-30 7.0 1.2 1960-OCT-02 10 2019-FEB-11 6.5 1.2 2002-OCT-08 11 2016-OCT-29 6.3 0.7 2003-SEP 12 1977-SEP-12 6 2 2003-NOV-01 13 2017-OCT-13 5.1 0.7 2008-JAN 14 2012-OCT-05 4.2 1.3 2009-NOV-11 COMMUNICATING FLOOD RISK
Flood Categories are used to communicate general impacts expected by incoming storms
MAJOR: Extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations.
MODERATE: Some inundation of structures and roads near stream. Some evacuations of people and/or transfer of property to higher elevations.
MINOR: Minimal or no property damage, but possibly some public threat.
From NWS website:
https://w1.weather.gov/glossary/index.php?word=Flood+Categories ILLUSTRATING FLOOD CATEGORIES
Flood categories are based on the height water would have to reach to impact structures and society Table of Table of storms infrastructure height
Elevation Elevation Vertical Uncertainty Elevation Feature Storm (ft MHHW) (ft MHHW) (ft) *Clinic first floor 13.6 1913-OCT-05 12 2 Dexter Roadhouse beach side 13 Highest recorded storm (still water) 12 1974-NOV-10 11 3 *Recommended building height 12.0 2013-NOV-09 10.5 1.2 *High school front door sill 11.1 1992-OCT-05 10.0 0.9 Major Drinking water 10.5 1945-OCT-28 9.1 1.4 Several buildings 10.5 2011-NOV-08 9 2 Fuel tanks 10.1 Major 10 2004-OCT-19 8.9 1.1 Lowest residences 8.8 2005-SEP-22 8.8 0.3 Roads in town 7.5 2016-DEC-30 7.0 1.2 Mod. Moderate 7.5 2019-FEB-11 6.5 1.2 Lowest building 7.0 Beach property 3.9 2016-OCT-29 6.3 0.7 Minor Minor 3.9 1977-SEP-12 6 2 2017-OCT-13 5.1 0.7 2012-OCT-05 4.2 1.3 Table of infrastructure height
Elevation Elevation Feature (ft MHHW) *Clinic first floor 13.6 Dexter Roadhouse beach side 13 Highest recorded storm (still water) 12 *Recommended building height 12.0 *High school front door sill 11.1 Major Drinking water 10.5 Several buildings 10.5 Fuel tanks 10.1 Major 10 Lowest residences 8.8 Roads in town 7.5 Mod. Moderate 7.5 Lowest building 7.0 Beach property 3.9 Minor Minor 3.9
Map of Flood Categories SOLVING THE PROBLEM
With this resource, you can: Quickly see the history of storms in a table Read about the storm impacts in a document See how forecasted storms might impact the community in a map
This has only been completed for Golovin and Hooper Bay. We are working on more locations, but it takes a lot of time to get it right! You can see pictures of storm impacts for many communities at the DGGS Photo Database: maps.dggs.alaska.gov/photodb Search “flood” and explore! BONUS SLIDES HOW DID THE USACE MODEL COMPARE TO OBSERVATIONS?
Elevation Vertical Top 10 surge events between 1954 and 2004 (Chapman et al. 2009) Rank Storm (ft MLLW) Uncertainty (ft) Maximum Surge 1 1913-OCT-05 13.7 2 Rank Starting Date (ft MLLW) 2 1974-NOV-10 12.7 3 11960-OCT-01 13.14 Mentioned in other sources, 3 2013-NOV-09 12.2 1.2 21974-Nov-10 12.74 4 1992-OCT-05 11.7 0.9 31970-NOV-26 10.32 no further details 5 1945-OCT-28 10.8 1.4 41978-NOV-26 10.05 6 2011-NOV-08 10.7 2 52004-OCT-15 10.02 Estimated: 10.6 ± 1.1 ft MLLW 7 2004-OCT-19 10.6 1.1 61966-NOV-14 9.96 8 2005-SEP-22 10.5 0.3 71996-OCT-25 9.33 9 2016-DEC-30 8.7 1.2 81975-AUG-25 8.74 10 2019-FEB-11 8.2 1.2 91965-NOV-12 8.15 11 2016-OCT-29 8 0.7 101985-NOV-06 8.12 Not mentioned in any sources 12 1977-SEP-12 7.7 2 13 2017-OCT-13 6.8 0.7 14 2012-OCT-05 5.9 1.3 1900-SEP-12 - - 1946-OCT-25 - - 1960-OCT-02 - - 2002-OCT-08 - - 2003-SEP - - 2003-NOV-01 - - 2008-JAN - - 2009-NOV-11 - - Using Forecast Tools 2011 – no dam
The community can build earthen dams to prevent flooding
2017 – dam!
Golovin, Alaska Flood impact without barrier Flood impact with barrier
Flood Height (ft MHHW) 0 1,000 Feet Flood Height (ft MHHW) 0 1,000 Feet 1.3 - 3.3 1.3 - 3.3 0 200 Meters 0 200 Meters Minor 3.4 - 7.2 Minor 3.4 - 7.2 Moderate 7.3 - 8.5 Moderate 7.3 - 8.5 Golovin Golovin Major 8.6 - 17.3 ± Major 8.6 - 17.3 ±