DISASTER 101 – FLOODING

When most people think of natural disasters, the first thing to come to mind is not likely flooding. However, flooding is the most common natural disaster. Flooding occurs in all 50 states, accounts for 40% of natural disasters, averages 5 billion dollars in damage each year, and claimed an average of 75 lives per year over the last 30 years.

Worldwide, statistics are similar.

According to the 30 year average, flooding is responsible for the most weather-related fatalities.

TYPES OF FLOODING

River and Lake Flooding

River and lake flooding is probably what most people envision when they think of floods. Heavy rainfall or snowmelt can cause water levels to rise overflowing banks and levees. River flooding is common in the Midwest as rain and snowmelt swells the tributaries that feed into larger rivers downstream. Once the water level crests the river banks, the area that is inundated can be widespread. Low lying areas, saturated soils, and urban areas can further exacerbate the effects of the overflow and take days to dissipate.

California experienced flooding in February when a weekend of storms increased runoff from Anderson Lake and flooded low-lying areas of San Jose. The early year storms also prompted the evacuation of over 88,000 people near the weakened Oroville Dam.

In May of 2017, heavy rainfall over the Midwest caused widespread flooding. Nearly 15 inches of rain fell over multiple states, saturating soils, and swelling multiple rivers above historic levels. Numerous levees were breached which flooded towns causing an estimated $1.7 billion dollars in damages to homes, businesses, and infrastructure.

40% of all natural disasters are flooding.

Coast Guard overflight of South Carolina flooding

Coastal Flooding and Storm Surge

A form of flooding happens regularly along coastlines due to the cycle of rising and lowering tides. Tides are a regular rise and fall of sea level caused by the gravitational interplay of the sun, moon, and earth. Occasionally, these tides can be exceptionally high. An increase of just a few feet is more than enough for tides to breech natural and man-made barriers. Many coastal cities are very near, or in some cases lower than, sea level making them especially prone to any change in sea level.

Storm surge can also cause extreme coastal flooding. The surge develops during severe weather, hurricanes, and tropical storms raising sea level as much as 25 feet. Sea level rise is the result of the low atmospheric pressure found in these storms which has a similar effect on sea level rise as the gravitational pull on tides. High winds common with these storms also cause large waves to batter the coast and push water farther inland. In worst case scenarios, the storm surge strikes the coast during a high tide cycle, increasing the flooding exponentially. Storm surge flooding is responsible for 90% of hurricane related deaths and the majority of the damage to structures.

In August of 2017, Hurricane Harvey alone caused over $125 billion dollars in damage and killed 89 people. The majority of the devastation caused by Harvey was a direct result of the widespread flooding of the Houston area.

Flash Floods

Flash floods can result from a variety of causes, but the common denominator is that they develop quickly and are normally caused by heavy rainfall. These floods can also be the result of snow melt, dislodged ice, inadequate urban drainage, or dam breaks. The actual volume of water carried in a flash flood is usually less than other flood types but the water is channeled down confined spaces which causes it to move with devastating force and speed. Because of this speed, flash floods are very dangerous, easily carrying mud, rocks, and trees in its flow. A Weather Channel article stated that, “water flowing at 7 mph has the equivalent force per unit area as air blowing at EF-5 tornado wind speed.” Whereas, “water moving at 25 mph has the pressure equivalent of wind blowing at 790 mph, faster than the speed of sound.”

 

BASIC SAFETY AND PREPAREDNESS

Ready.gov provides many helpful tips.

Be Mindful

  • Stay tuned to phone alerts, TV, or radio for weather updates, emergency instructions, or evacuation orders.
  • Avoid walking or driving through flood waters. 6 inches of moving water can knock a person over, and one foot of moving water can sweep a vehicle away. According to the Environmental Protection Agency, the leading cause of flood-related injury and death is individuals attempting to drive through flood waters.
  • Do not drive over bridges that are over fast-moving floodwaters. Floodwaters can scour foundation material from around the footings and make the bridge unstable.
  • If there is a chance of flash flooding, move immediately to higher ground.

Protect your home

  • Know your flood risk, avoid building in flood plains, and consider buying flood insurance.
  • If you have to evacuate due to flooding, and if safety permits, turn off all the utilities to your home and attempt to move valuables to the highest possible level.

SOURCES

https://www.ready.gov/floods
https://www.nssl.noaa.gov/education/svrwx101/floods/types/
https://www.ncdc.noaa.gov/billions/events/US/2017-2018
http://www.floodsite.net/juniorfloodsite/html/en/student/thingstoknow/hydrology/floodtypes.html
https://weatherology.com/articles/106/The+Dangers+of+Flash+Floods.html
https://weather.com/storms/severe/news/power-flood-water-20130704
https://www.livescience.com/23913-flood-facts.html

Blizzard, snow

Nor’easters Repeatedly Hammer the East Coast with Blizzard Conditions

Update: 03/29/2018 all four Nor’Easter storms have passed.

As the forecasts indicated when this blog was initially written, a 4th Nor’easter storm hit the east coast. Winter storm Toby began to run its course on the landscape in the early morning hours of Wednesday March 21st. After Toby had passed the snow accumulation was shocking in the areas that were hit hardest. Areas of Pennsylvania received over a foot of snow in the short period of time that Toby was over the area. Central Park in New York City recorded 8 inches of snow while some areas in Long Island, New York reported up to 20 inches from the weather system. Unlike the previous three Nor’easter storms that occurred in the weeks leading up to Toby, this storm actually impacted the entirety of the east coast in varying levels. Upon the arrival of Toby, parts of Florida and Georgia both received heavy hail in some areas along with drastically increased wind speeds along the coast. This storm actually triggered tornado watches in the northern portions of Florida. Have storms of this magnitude hit the east coast in such a short period of time before?

Even though having four powerful Nor’easters hit the east coast in such a rapid succession is uncommon, it has happened before. Actually, as recently as 2015 three Nor’easters struck the same area distributing similar weather patterns that were seen with the four storms that have hit this month. In 2015 the series of Nor’easters started with Winter Storm Lola (January 23-24 2015), and then came Winter Storm Juno (Jan. 26-28, 2015), Finally Winter Storm Linus (Feb. 2, 2015) made its arrival in the area. These storms broke records in the City of Boston, Massachusetts for the most accumulation of snow during winter that has been recorded to date.

Original Post

The word Nor’easter has been quite prevalent in the media for the last two and a half weeks as a description for the type of storms that have been wreaking havoc across the east coast. Nor’easter storms get their name from the predominant wind direction that the system gets pushed in from. These storms are pushed from the Atlantic Ocean into the East Coast of the U.S., carrying massive amounts of water with them. A typical Nor’easter storm would consist of gale force winds (around 40 miles per hour and up), rough seas off the east coast, and massive amounts of precipitation in the form of rain or snow. The way these storms form and become so powerful is quite fascinating. The polar jet stream transports cold arctic air down over the United States and meets with the warm air of the jet stream located over the gulf coast. This collision of colder air over land and warmer moist air over the Atlantic Ocean is the driving force that creates these cyclonic storm systems. Nor’easters have been seen throughout all seasons of the year, but they are the most common and the most powerful between the months of September and April.

Satellite, Imagery

This Satellite imagery displays what the formation of a Nor’easter storm looks like from space.

Current Status of the East Coast

            Yesterday, the third Nor’easter storm made landfall on the northern reaches of the east coast. The series of storms started on March second when winter storm Riley brought widespread precipitation in the forms of heavy rain and snow that earned the declaration for blizzard condition warnings in many counties. The storm hit the coast of New England with a force that would cause massive destruction. Storm surges brought about large scale coastal erosion, along with flooding of many coastal areas. At the peak of the first storm, over 1 million residents of New York, New England, and North Carolina were without power for an extended period of time. Riley was followed shortly after by winter storm Quinn. Quinn had a similar impact to the east coast, which was still trying to recover from the first storm. During this second large storm, thousands of flights had to be cancelled due to unsafe flying conditions for large passenger carrying aircraft. This storm system again passed through, leaving an absurd amount of snowfall, high wind speeds, and unsafe travel conditions. Finally, winter storm Skylar made its way to the east coast during the evening hours on Tuesday. Similar to the previous two storms that have occurred in the last two weeks, this powerful weather system left in its wake an abundance of rain and snow, accompanied by gale force winds and loss of power for hundreds of thousands of residents in the area. The storm surges seen during these storms are similar to what occurred during some of the hurricanes that hit the southern coast of the U.S. this year. You can read about the damages that occurred during these incidents in RedZone’s previous blog “Hurricanes Harvey and Irma batter Southern US”.

GIS, Snow forecast

This map provided from FEMA shows the snow levels that are expected from winter storm Skylar.

Forecast for the East Coast

Unfortunately, forecasts for the east coast are looking like residents “aren’t out of the woods yet” when it comes to heavy winter storms. The discrepancies between the American and European forecast models are mainly surrounding the formation of this storm system once both air masses collide on the east coast. What is known is that another wave of cold air is making its way across the lower 48 states through this weekend. The cool air will arrive on the east coast late Monday night into Tuesday of next week. Due to the amount of time it will take for this system to make its way over to the east coast, meteorologists cannot say with certainty how powerful this storm will be. As the week progresses, the models will become more accurate, providing more details on the occurrence of this possible Nor’easter formation.

 

Sources: https://www.weather.gov/safety/winter-noreaster

https://weather.com/storms/winter/news/2018-03-01-winter-storm-riley-noreaster-high-winds-coastal-flooding-heavy-snow

https://weather.com/storms/winter/news/2018-03-14-snow-ice-west-midwest-east-mid-march

https://content.govdelivery.com/attachments/USDHSFEMA/2018/03/13/file_attachments/972703/FEMA%2BDaily%2BOps%2BBriefing%2B03-13-2018.pdf

https://weather.com/storms/winter/news/2018-03-19-winter-storm-toby-fourth-march-noreaster-northeast-snow

https://weather.com/storms/winter/news/2018-03-20-four-noreasters-three-weeks-winter-storm-quinn-riley-skylar-toby

road closure thumbnail

Incoming Heavy Rains Increase Debris Flow Risk Yet Again

The National Weather Service (NWS), Los Angeles Office is warning the region that sustained heavy rains are incoming for the majority of the rest of the week. The beginning of the rain is set to arrive today (Tuesday) and last well into Thursday. The “atmospheric river” storm is expected to bring between 5 and 10 inches of rain in the foothills and mountains, significantly more total rainfall than the 1/9 debris flow, which brought between 3 and 6 inches to the region. The NWS says this storm is projected to have the heaviest rainfall and the longest duration of this winter storm season. “All models indicate high confidence in rainfall totals and the duration of the storm.”

Rainfall forecast through 3/26

National Weather Service Precipitation forecast for the Greater Los Angeles and Santa Barbara Areas through the weekend. Recent Fires are seen in black on the map as worry grows about debris flow potential.

Debris Flow Risk for Santa Barbara County Burn Areas

We caught Monday’s press conference from Emergency Officials with Santa Barbara County, who are stressing the seriousness of the renewed threat flooding and especially of debris flow.  Opening the discussion, Meteorologist, Mark Jackson warned, “A key worry with this storm is rainfall rates that can trigger debris flows. It’s not necessarily the total amount of rain that occurs; it’s how fast that rain falls.” Well, the latest meteorological models by the National Weather Service indicate that there is potential for rainfall intensity of between .5 to .75 inches per hour, which is enough to trigger debris flows at any time during the storm.

Recent Burn Areas tweet

NWS Los Angeles warning via tweet today that debris flows near recent fires are likely across the region

As a result, many residents downslope of Thomas and other fires in the region (seen as black in the map above & highlighted in the tweet below) have been evacuated or at least cautioned. Santa Barbara County is also managing and updating an evacuation map found here.  In addition, Rob Lewin, director of the Santa Barbara County Office of Emergency Management, warned the amount of rain and the intensity is enough to cause flooding even without the impact of the recent fires. “We could experience localized flooding and road closures which are not isolated to the burn areas. The threat of rock falls, mud slides and debris flow is high,” he noted.

“A key worry with this storm is rainfall rates that can trigger debris flows. It’s not necessarily the total amount of rain that occurs; it’s how fast that rain falls.” – Mark Jackson, NWS Meteorologist

Storm Facts:

  • Heaviest Rainfall for Ventura County to San Luis Obispo County is expected Wednesday afternoon to Thursday morning (March 21 – March 22)
  • Heaviest Rainfall for LA County is expected Thursday into Thursday Night (March 22)
  • Rainfall totals for the Coasts/Valleys will be 2-5 inches, for the Foothills/Mountains more like 5-10 inches.
  • Flash flooding and significant debris flows near recent burn scars are likely
  • Urban and small stream flooding expected
  • Slight chance of main stem river flooding
  • Road closures anticipated due to rock fall in the mountains
  • Residents in the Extreme and High Risks areas of Santa Barbara County are required to evacuate at noon on Tuesday (March 20)
  • Mandatory evacuations prompted for areas below the Thomas, Whittier, and Sherpa Fires

Sources:

National Weather Service

Santa Barbara County Emergency Services

KSBY News

Blizzard, snow

Nor’easters Repeatedly Hammer the East Coast with Blizzard Conditions

The word Nor’easter has been quite prevalent in the media for the last two and a half weeks as a description for the type of storms that have been wreaking havoc across the east coast. Nor’easter storms get their name from the predominant wind direction that the system gets pushed in from. These storms are pushed from the Atlantic Ocean into the East Coast of the U.S., carrying massive amounts of water with them. A typical Nor’easter storm would consist of gale force winds (around 40 miles per hour and up), rough seas off the east coast, and massive amounts of precipitation in the form of rain or snow. The way these storms form and become so powerful is quite fascinating. The polar jet stream transports cold arctic air down over the United States and meets with the warm air of the jet stream located over the gulf coast. This collision of colder air over land and warmer moist air over the Atlantic Ocean is the driving force that creates these cyclonic storm systems. Nor’easters have been seen throughout all seasons of the year, but they are the most common and the most powerful between the months of September and April.

Satellite, Imagery

This Satellite imagery displays what the formation of a Nor’easter storm looks like from space.

Current Status of the East Coast

            Yesterday, the third Nor’easter storm made landfall on the northern reaches of the east coast. The series of storms started on March second when winter storm Riley brought widespread precipitation in the forms of heavy rain and snow that earned the declaration for blizzard condition warnings in many counties. The storm hit the coast of New England with a force that would cause massive destruction. Storm surges brought about large scale coastal erosion, along with flooding of many coastal areas. At the peak of the first storm, over 1 million residents of New York, New England, and North Carolina were without power for an extended period of time. Riley was followed shortly after by winter storm Quinn. Quinn had a similar impact to the east coast, which was still trying to recover from the first storm. During this second large storm, thousands of flights had to be cancelled due to unsafe flying conditions for large passenger carrying aircraft. This storm system again passed through, leaving an absurd amount of snowfall, high wind speeds, and unsafe travel conditions. Finally, winter storm Skylar made its way to the east coast during the evening hours on Tuesday. Similar to the previous two storms that have occurred in the last two weeks, this powerful weather system left in its wake an abundance of rain and snow, accompanied by gale force winds and loss of power for hundreds of thousands of residents in the area. The storm surges seen during these storms are similar to what occurred during some of the hurricanes that hit the southern coast of the U.S. this year. You can read about the damages that occurred during these incidents in RedZone’s previous blog “Hurricanes Harvey and Irma batter Southern US”.

GIS, Snow forecast

This map provided from FEMA shows the snow levels that are expected from winter storm Skylar.

Forecast for the East Coast

Unfortunately, forecasts for the east coast are looking like residents “aren’t out of the woods yet” when it comes to heavy winter storms. The discrepancies between the American and European forecast models are mainly surrounding the formation of this storm system once both air masses collide on the east coast. What is known is that another wave of cold air is making its way across the lower 48 states through this weekend. The cool air will arrive on the east coast late Monday night into Tuesday of next week. Due to the amount of time it will take for this system to make its way over to the east coast, meteorologists cannot say with certainty how powerful this storm will be. As the week progresses, the models will become more accurate, providing more details on the occurrence of this possible Nor’easter formation.

 

Sources: https://www.weather.gov/safety/winter-noreaster

https://weather.com/storms/winter/news/2018-03-01-winter-storm-riley-noreaster-high-winds-coastal-flooding-heavy-snow

https://weather.com/storms/winter/news/2018-03-14-snow-ice-west-midwest-east-mid-march

https://content.govdelivery.com/attachments/USDHSFEMA/2018/03/13/file_attachments/972703/FEMA%2BDaily%2BOps%2BBriefing%2B03-13-2018.pdf

Burn Scar

Debris Flow Devastates Montecito, CA Immediately After The Thomas Fire

While the threat of the Thomas fire just recently diminished in Ventura and Santa Barbra Counties, residents were weary to hear that they are now being threatened by mudslides originating from within the burn area. Rain started Monday afternoon in the areas of Santa Barbara and Ventura Counties, with the peak rainfall being around 2:30 AM Tuesday morning. The rain came down in amounts up to an inch per hour over the burned area, which the incident commander reported as being a critical factor in the amount of sediment and debris being carried by this amount of water. The devastating debris flow ranged from Cold Springs Canyon to Toro Canyon, and wreaked havoc all the way down to Highway 101. The debris flow was so strong in some locations that it pushed homes off of their foundations and carried them several hundred feet.

First responders have been preparing for this incident since Monday morning by preemptively staging resources in the areas that were forecasted to be impacted the most severely. This strategic placement of resources was followed by officials releasing evacuation zones. The warning stated that all residents within mandatory evacuation zones should leave by 12 noon on Monday in preparation for the heavy rains that were forecasted for the area. Since the early morning hours of Tuesday, first responders have been in a search and rescue mode: still actively engaged in performing helicopter and contact rescues. The threat from this debris flow still remains and first responders are warning residents to stay away from the area if at all possible.

Debris flow

An explanation of a debris flow, and its power.

 

Over the last couple weeks of the Thomas Fire the Federal Burned Area Emergency Response (BAER) Team has been evaluating the blaze’s impact to the fire area and watersheds by predicting debris flow hazards should rains like this impact the area. The orange, red, and dark red areas were determined to have the highest probability of debris flow during a heavy rain event. The BAER team is currently embedded with the Santa Barbara and Ventura Office of Emergency Services to assist them in implementing response plans for communities downstream of the fire.

BAER Debris Flow

The map above displays estimates of the likelihood of debris flow (in %), potential volume of debris flow, and combined relative debris flow hazard.

Santa Barbara/Ventura Flooding at a Glance

  • 17 confirmed deaths related to the storms (These numbers are subject to change as the incident continues)
  • 13 missing people
  • At least 25 injured
  • 50 rescues via helicopter hoists have been performed during today’s search and rescue operations.
  • 1-6.5 inches of rainfall over the Thomas Fire area.
  • Search and rescue efforts still remain priority with approximately 75 percent of the primary search completed in the debris flow area.

If you liked the material in this blog, you can read similar material RedZone has covered here.

Sources

http://www.cnn.com/2018/01/09/us/southern-california-evacuations-rain-flooding/index.html

http://www.latimes.com/local/lanow/la-me-ln-rainfall-mudflow-20180109-story.html

http://santabarbara.onerain.com/map/?sensor_class=10|2880&view_id=5&view=8bc6e88f-eeab-4281-9d92-3d723016e945

https://landslides.usgs.gov/hazards/postfire_debrisflow/detail.php?objectid=178

Aerial photo over Kynsna area (Source: South African Red Cross)

Wildfires Rage Across South Africa’s Cape After Massive Winter Storm

Hundreds are left homeless and thousands remain evacuated after the strongest winter storm in decades assaulted Cape Town, South Africa, and continued across the southern region of South Africa known as the Western Cape. Numerous lightning strikes associated with the massive storm ignited wildfires that raged across hillsides, fueled by gusting and strong winds, even as nearby areas began to flood and were drenched by rain. Tuesday evening, June 6th, the storm began to impact the Western Cape. By Wednesday, thousands of residents along the major roadway N2, famously known as the “Garden Route”, were evacuated as wildfires blazed toward nearby neighborhoods. As of June 8th, 4pm PDT, nine deaths are attributed to the storm, home collapses, and wildfires.

Storm Impact & Wildfires in Area around Cape Town and Knysna (Source: Google Earth)

Storm & Wildfire Impacted Area around Cape Town and Knysna (Source: Google Earth)

Current Situation

The local media is referring to this as the “mother of all storms”. A compounding factor to the devastating impact to the region is the already poor housing covering much of the area. Shanty towns burn quickly and can also collapse simply due to the strength of the winds. Flood waters also washed away several communities due to non-permanent construction. Part of the evacuation process included a local hospital in Knysna had to move all personnel and patients due to the approaching wildfires. The rain now falling on the Knysna area will assist firefighting efforts to get the wildfires under control; however, the additional rains will increase the possibilities for mudslides in the area.

Activity of Wildfires in last 48 hours, centered on Knysna (Source: Advanced Fire Information System Viewer – AFIS)

Wildfire activity in last 48 hours, centered on Knysna (Source: Advanced Fire Information System Viewer – AFIS)

Recovery & Outlook

So far, reports indicate more than 150 structures were destroyed throughout 20 suburbs. Cape Town, fortunately, has restored approximately 90% of its power. Across the impacted area, staff are opening shelters and resource centers to assist those displaced. The rains received may help with a fraction of the drought situation, but Level 3 water restrictions remain in place. Wetting rains over a longer duration are needed to truly have an impact. Local volunteers are collecting donations of items such as food, water, blankets, and other basic necessities for those affected by this disaster.

Aerial photo over Kynsna area of wildfires (Source: South African Red Cross)

Aerial photo over Kynsna area (Source: South African Red Cross)

Read further

Live update stream: http://www.news24.com/SouthAfrica/News/live-knysna-evacuation-underway-20170607

http://www.bbc.com/news/world-africa-40199270

http://www.accuweather.com/en/weather-news/powerful-winter-storm-kills-at-least-eight-in-cape-town/70001884

http://www.cnn.com/2017/06/08/world/south-africa-fires/

http://www.aljazeera.com/news/2017/06/storm-kills-displaces-thousands-cape-town-170608052748704.html

Pfieffer Bridge in Big Sur is impassible

Crumbling Bridge Splits Big Sur Community

The Central Coast of California has been a hot spot for activity this year. The normally quaint and quiet Big Sur area is one of the wettest and most rugged in all of Coastal California. In the past year, the area has seen the region’s largest ever fire (Soberanes), and its highest winter rainfall accumulation in over a decade. Although the latest winter storms in February have pulled the area out of a six year long drought, it also has also–quite literally–split the Monterey County community in two.

Heavy Rains Damage Monterey County Roads and Bridges

Since the beginning of the year, the well-traveled section of Highway 1 through Big Sur has seen over 15 inches of rain, and its steep hillsides have endured numerous land and mud slides. Consequently, a 50-mile stretch of the highway has been closed to facilitate a major cleanup effort for the better part of a month. What’s worse is that the Pfeiffer Canyon Bridge (in the Soberanes Fire area) has actually buckled due to the support columns moving from heavy runoff during early February’s rain events. Highway 1 has had a hard closure there, making the highway impassible since February 12th.

Pfieffer Bridge in Big Sur is impassible

The Pfeiffer Bridge in Big Sur has been impassible since February 12, 2017

As a result, tourists have had to deal with very long detours and local residents have been left stranded. The bridge’s support columns have shifted a significant distance from their operational location and have made the bridge unable to support the minimum mandated weight. Cal trans crews are working on plans to demolish the bridge into 3 manageable sections for removal and then begin the yearlong process of building a new structure. Crews have spent the weeks since the bridge damage discovery moving demolition equipment into place using helicopters.

On March 13th, the demolition process began with a 6,000 pound wrecking ball. After a few hours of work the crews realized that in the current configuration, the wrecking ball could not get enough downward force to break up the bridge. Parts were ordered to change the configuration and demolition personnel were set to try again on March 15th.

Impact to Big Sur Residents Could Last Months

While the road crews focus all their efforts on getting more sections of the Highway open, around 400 residents have been unable to drive from their homes, relying only on their supplies at home. Due to the lengthy closure, affected homeowners have run low on food and water. Some are resorting to travelling by foot to get hundreds of pounds of food while others are utilizing rations that have been flown into locations by helicopter.

A plan is underway to actually build a new hiking trail (1/2 mile foot path) that can be used by homeowners to get around the Pfeiffer Bridge closure. The trail is being constructed by California Conservation Crews and numerous volunteers, and will take some time to complete. The use of the trail will be limited to residents and can only be used during specific hours.

For emergency responders, the closure situation causes a different problem in terms accessing residences during future emergency situations. The new bridge will take months to construct and the Big Sur Volunteer Fire Brigade is responsible for the safety of residents on both sides of the closure. As a solution, the brigade has actually split into two response areas but, at this point, cannot access all of their response territory. Currently, there is a contingency plan in place to use a Medivac helicopter to get people out that may need medical attention. The Big Sur Medical Center, which is also affected by the closure, has continued to receive medical resupply, including daily prescriptions that area residents need. The sense is that local authorities seem confident in the contingency plan in place. They have said numerous times that they will be able to provide emergency services to all remote areas.

san jose flood

Areas of San Jose Flood After Nearby Dam Overflows

Low-lying areas of San Jose have flooded due to increased runoff from Anderson Lake after a weekend of multiple rain storms.  The lake, which is 15 miles southeast of San Jose, had been slowly filling to capacity.  Water levels eventually spilled over Anderson Dam into Coyote Creek which flows northwest, directly into the heart of San Jose.  The influx of extra runoff caused the creek to crest at a height of over 13 feet, causing widespread flooding to many areas between Gilroy and San Jose.

The worst of the Flooding appears to be centered on the Nordale neighborhood of San Jose. Many homes and streets in that area are under water. As of Tuesday afternoon (2/21), 186 residents had been evacuated via boat and helicopter. San Jose mayor Sam Liccardo announced that up to 500 more residents were under voluntary evacuation as the creek continues to receive the dam’s excess water. The city itself saw over two more inches of rain on top of a very wet winter. The area has had measurable precipitation on all but five of the days so far this month.

San Jose Flood at a Glance

• Recent storms have caused Coyote Creek to become a spillway for Anderson Reservoir, which is overflowing beyond its capacity.
• Rescue efforts have been focused on the Nordale Neighborhood in the heart of San Jose where dozens of people were aided to safety by boat and helicopter.
• Officials are concerned with potential contamination of the water due to potentially overflowing sewage lines, oil and gas from vehicles trapped in the water, or household chemicals that may have leaked into the flood waters.
• San Jose’s mayor announced a voluntary evacuation for low-lying areas along Coyote Creek between the I-880 and the Capitol Expressway due to the risk of continued flooding.
• So far, 16 of February’s 21 days have involved measurable precipitation in San Jose.
• Multiple zoo animals had to be relocated in the nearby Happy Hollow Park.

San Jose Flood Outlook

The persistent rains are forecasted to cease overnight, and dryer weather is expected at least through Saturday evening.  Despite the release of countless gallons of water, Anderson Dam will still sit well above its recommended level of 68% for the foreseeable future.  Evacuated residents will have to wait until the floodwaters subside to return to their homes, and may be delayed by the potential of polluted water.

In the past few weeks, most of the rainfall worries have been centered on Butte County and the Oroville Dam Spillway situation.  If the relentless rain trend continues, reservoirs across the state of California could see further rising levels, which in turn could increase the risk of more flooding events.

Sources: Weather Channel, ABC7 News: Bay Area, Wunderground

Heavy Rain Event Underway for Southern California

The West Coast is bracing for yet another heavy rain event. Luckily, each storm this winter has slowly helped the previously dire drought situation, which covered most of the State of California. This storm, however, will bring sustained rain from Southern Oregon all the way south through San Diego. The worst of it, though, has its sights set on Southern California, arriving late Thursday. Meteorologists are predicting the region may see the heaviest precipitation in six years, including up to 8 inches in some areas. The National Weather Service in Los Angeles is saying that daily rain records are likely to be set on Friday. Strong winds, up to 50 or 60 mph, are also expected. As the heavy rain nears, local authorities are preparing for widespread road closures, power outages, tree damage, flash flooding, and coastal flooding.

Storm Total Rain through Saturday for the Los Angeles Area

Projected Rainfall for the next 36 hours from the National Weather Service out of Los Angeles

Mudslide Potential

There will also be a real potential for mudslides in some areas, especially within the several recent burn scars in the region that align with the heavy expected rain (seen in the map below). Approximately 180 homes in Duarte have already been evacuated ahead of the storm due to their close proximity to an expected debris flow from the Fish Fire burn scar. Similarly, residents in Glendora, near the Colby Fire burn area, were told to remain “on alert”. Local officials are likely being cautious as annually the CDC reports 25-50 deaths a year from mudslides on average in the US.

Recent Burn Scars all to receive 3+ inches of heavy rain

Map showing where 2016’s recent burn scars shown against the forecasted rain totals for Southern CA

Northern California to See Heavy Rain Too

While Northern California will not see as widespread a downpour, that region will also see significant rainfall totals. Due to the incoming storm, the Lake Oroville situation remains troubling, despite the fact that Butte County Officials have technically lifted the evacuation orders for residents. The lake has lowered 30 feet since its peak during the last storm.  Officials hope they can relieve the reservoir of another 30 before the rains arrive again (the current rate is reportedly one foot every three hours). Unfortunately, the Oroville watershed is forecast to receive another 5-8 inches of rain itself by the end of the weekend, which could swell the lake to complicated levels again. Fortunately, the rain has continued to help swell California’s reservoirs statewide to near or, in most cases, over their historical average level.

Additionally, heavy snow is also projected for the high elevations and Sierra Nevada Range. An additional two feet of snow is forecast to add to the already above-average snowpack throughout the region. As an example, Eastern Sierra’s Mammoth Mountain, which has already received a whopping 432 inches of snow this winter, is expecting another 24-32” by Wednesday night.

Sources

National Weather Service, The Weather Channel, AccuWeather, LA Times, NOAA

Lake Oroville Dam Verges on Collapse

Officials released water from an emergency spillway at Lake Oroville that has not been used since the dam was built in 1968. Oroville Dam is the highest dam in the nation and stores water in California’s second largest reservoir. Crews have been closely monitoring the water flow during this historic winter that has filled up most of Northern California’s lakes and reservoirs, pulling much of the state out of its 6-year drought.

Almost 200,000 Evacuated in Lake Oroville Flood Plain

On Sunday, February 12th, 2017, the California Department of Water Resources decided to open the emergency spillway after a large hole in the main spillway developed and debris blocked outlets, causing water levels to reach the emergency spillway’s maximum capacity. As water cascaded over the concrete wall, dirt began to wash downhill into the valley below. The movement of the hillside caused officials to worry that a complete failure was imminent, and they began California’s largest mass evacuation since the 2007 wildfires in Southern California. Nearly 200,000 people that live within the established flood plains were asked to vacate. As of February 14, at 15:00 PST, all evacuation orders had been lifted, but residents are still on edge as more winter storms approach the region.

Lake Oroville Dam

The area below the Lake Oroville emergency spillway (As of 2/13/2017). (Photo courtesy of http://www.latimes.com)

While residents were told they had an hour to evacuate the area, officials worked on a plan of how to prevent a total failure of the emergency spillway. Rushing water was washing away the anchor that held the emergency spillway’s concrete foundations in place. As the water pushed over the dirt, it caused the hillside to crumble and move downslope, weakening the earth that holds back millions of gallons of water. Water moved at 100,000 cubic-feet-per-second (cfs) over the main spillway, as officials attempted to drop water levels below the emergency spillway’s banks.  Their goal was a decrease of at least 50 feet so as to minimize structural damage in the short term, and prepare for more winter storms and snow melt in the coming months. On Monday, February 13, 2017, helicopters began dropping bags of boulders over the heavily eroded ground in an attempt to stop more erosion and strengthen areas below the emergency spillway.

Water Levels Down, but Not Completely Safe Yet

Though no more water flows over the emergency spillway, 100,000 cfs of water continues to rage down the main spillway, and evacuees have no timeframe for when they can return home. As of 1pm PT on February 13, 2017, officials reported that water levels were 9ft below the emergency spillway’s breaching point, and helicopters continued to provide erosion control measures to the hardest hit areas. The most recent estimate for repairs to the spillway is upwards of $200 million, and these repairs cannot begin until water levels are stabilized.

Sources:

http://www.latimes.com/local/california/la-live-updates-oroville-dam-butte-county-sheriff-defends-evacuation-1487022068-htmlstory.html

http://www.sfgate.com/bayarea/article/Oroville-Dam-emergency-spillway-in-use-for-first-10925628.php

https://calfire.blogspot.com/2017/02/