Full Text
Part 3 City of Redmond Hazards Mitigation Plan • 123 Hazard Identification and Risk Assessment Hazard Identification and Risk Assessment Part 3 CHAPTER 10 - Heat Waves Heat Wave Risk Assessment This plan is an update of the 2004 City of Redmond Hazard Mitigation Plan (HMP). Although it is an update, this document has been redesigned so that it looks, feels, and reads differently than the original. This is due to several factors: new hazard information has become available that drives new definitions of risk, the City has matured and new capabilities are now available, and the new format will allow readers to more easily understand the content. In addition, the 2004 HMP included several action items that have been completed, creating an opportunity for developing new mitigation strategies. 10.1 Identifying Heat Wave Hazards A heat wave is commonly defined as a period of abnormal, uncomfortably hot weather. The maximum daytime Heat Index (HI) defines a heat wave by combining temperature with humidity to calculate how hot it feels. Locally, daytime temperatures in the 90s are a problem. Since the Pacific Northwest does not typically experience such extreme temperatures, people do not have air conditioning and bodies are stressed by several days of heat in the 90s or above. Periods that do not cool down at night are particularly harmful. Since the 1970s, an average of three to four deaths occur annually. In 1992, an excessively warm summer was linked to 50-60 deaths.111 Heat waves are typically more severe in urban areas with stagnant atmospheric conditions and in areas with high levels of humidity. Heat waves occur every summer in many parts of the United States. Increased high temperatures may also lead to wildfires and drought. 10.2 Profiling Heat Wave Hazard Events A. Location In the event of a heat wave, all areas of Redmond will be affected. Redmond’s temperate climate and suburban setting are generally not conducive to heat waves. The general lack of residential air conditioning will increase the impacts of irregularly high temperatures. B. Timing and Duration Heat waves occur in the summer months and generally can be predicted through weather monitoring. Two consecutive days of temperatures above 90°F triggers the National Weather Service Heat Advisory. Typical hot weather in Redmond is in the low 90°F range and generally lasts for a maximum of four days.112 111 National Weather Service, “Heat Wave: A Major Summer Killer,” National Oceanic and Atmospheric Administration (NOAA), 112 Office of the Washington State Climatologist, Temperature data from 1999-2008, Courtesy of Karin Bumbaco. Assistant State Climatologist. ---PAGE BREAK--- Part 3 City of Redmond Hazards Mitigation Plan • 124 Hazard Identification and Risk Assessment Hazard Identification and Risk Assessment Part 3 CHAPTER 10 - Heat Waves C. Severity According to temperature data from the Office of the Washington State Climatologist, the average Redmond area temperature is 76°F. The highest summer temperatures in 2000-2008 in the Redmond area are displayed in Figure 7. In 2006 and 2007, Redmond experienced historic highs of 95°F.113 Redmond’s record high temperature is below the National Weather Service’s alert temperature of 105°F. However, due to the generally mild climate, several days in the 95°F range would have a significant impact on the City. D. Frequency Previous Occurrences Redmond has never experienced a heat wave as defined by the National Weather Service. However, Redmond has experienced temperatures in the upper 90s that have lasted for several days, in both 1992 and in 2009, with a new record high temperature of 103 degrees. Probability of Future Events: Climate change trends will increase the number of hot weather days in Redmond. Predictions indicate that average temperatures will increase 2°F by 2020.114 Temperature fluctuations will be more extreme, potentially increasing temperatures in the Redmond area to higher levels that would trigger a National Weather Service alert. Climate change information also suggests that increasing temperatures will affect urban and rural areas similarly. In the future, Redmond may not be insulated from heat waves as it has been in the past.115 10.3 Assessing Heat Wave Vulnerability 113 Ibid. 114 Climate Impacts Group, “Climate Change Scenarios,” University of Washington, http://cses.washington. 115 Climate Impacts Group, “Climate Change Scenarios,” University of Washington, http://cses.washington. Highest Temperatures Recorded from 2000 2008 94 96 Highest Temperatures Recorded from 2000 ‐ 2008 90 92 94 96 re Highest Temperatures Recorded from 2000 ‐ 2008 86 88 90 92 94 96 Temperature Highest Temperatures Recorded from 2000 ‐ 2008 Temperature in degrees Fahrenheit 82 84 86 88 90 92 94 96 Temperature Highest Temperatures Recorded from 2000 ‐ 2008 Temperature in degrees Fahrenheit 80 82 84 86 88 90 92 94 96 Temperature Highest Temperatures Recorded from 2000 ‐ 2008 Temperature in degrees Fahrenheit 80 82 84 86 88 90 92 94 96 Temperature Highest Temperatures Recorded from 2000 ‐ 2008 Temperature in degrees Fahrenheit Figure 7: Highest Temperatures Recorded in Redmond Area Source: Data from the Office of the Washington State Climatologist ---PAGE BREAK--- Part 3 City of Redmond Hazards Mitigation Plan • 125 Hazard Identification and Risk Assessment Hazard Identification and Risk Assessment Part 3 CHAPTER 10 - Heat Waves 10.3.1 Overview Currently, extremely high temperatures are rare in the Pacific Northwest and thus Redmond is not particularly vulnerable. However, as the climate changes, heat waves are an anticipated hazard. In the event of a heat wave in Redmond, human populations, the natural environment and energy systems may be affected. Since Redmond is unaccustomed to heat waves, temperatures in the 90s may have impacts, even though such an event would not trigger a National Weather Service alert. 10.3.2 Profiling the Vulnerabilities A. Man-made Built structures are not vulnerable to heat waves. B. Natural In the event of a heat wave, some crop growth may be impacted if the heat occurs during the plant’s early development stages. If a drought accompanies a heat wave, water shortages will impact crop and other vegetation growth. Extreme high temperatures may also increase the likelihood of wildfires. Heat waves can increase temperatures in streams and rivers, which could lead to changes in migration timing, reduce growth rates and reduce available oxygen for local fish species.116 C. Systems Extremely high temperatures will increase water usage. The water supply is vulnerable to overuse during a heat wave. High temperatures can soften of asphalt or buckle concrete. Such damage to the roadways would lead to regional transportation problems.117 D. Populations The body cannot easily compensate with overexposure to heat. Heat-related illnesses include fatigue, dehydration, heat 116 National Wildlife Federation,“A Great Wave Rising: Solutions for Columbia and Snake River Salmon in the Age of Global Warming,” http://www.nwf.org/GlobalWarming/pdfs/AGreatWaveRising.pdf. 117 Cooperative Institute for Research in the Atmosphere, “Impacts of Temperature Extremes,” http:// sciencepolicy.colorado.edu/socasp/weather1/adams.html. Retirement Homes and Low Income Populations HT_MAP2_CAS.mxd 06-07-09 Source: King County Major Roadways Retirement and Low Income Populations 3,000 0 3,000 1,500 Approximate Scale in Feet Map 32: Retirement Homes and Low Income Populations ---PAGE BREAK--- Part 3 City of Redmond Hazards Mitigation Plan • 126 Hazard Identification and Risk Assessment Hazard Identification and Risk Assessment Part 3 CHAPTER 10 - Heat Waves exhaustion and heat stroke. In a normal year, about 175 Americans die from the summer heat.118 Hazard Specific People without access to cooling devices such as air conditioning may be more vulnerable during a heat wave. Isolated Populations Since there will be little structural damage during a heat wave, people will not become isolated. Disabled Persons Disabled persons with compromised immune systems may have an increased risk. Elderly High temperatures require the human heart to work harder to pump blood toward the skin to help regulate body temperature. Elderly populations, especially those with heart conditions, will be more impacted by heat waves.119 Limited English Language Non-English speaking populations will not be particularly vulnerable to heat waves. Low-income Residents Low-income residents may be more impacted by heat waves if they do not have access to air-conditioning. 10.3.3 Analyzing Development Trends Development and paved surfaces increase local surface temperatures. Urban areas create localized “heat islands”; increased development in Redmond will amplify this effect. If heat waves are accompanied by water shortages, population increases will correlate to water demand. 118 National Weather Service, “Heat Wave: A Major Summer Killer,” National Oceanic and Atmospheric Administration (NOAA), 119 Cooperative Institute for Research in the Atmosphere, “Impacts of Temperature Extremes,” http:// sciencepolicy.colorado.edu/socasp/weather1/adams.html. Table 18: Likelihood of Heat Disorders Based on Temperature and Relative Humidity Source: National Oceanic and Atmospheric Administration, “National Weather Service Heat Index,”