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It’s been quite a week. My home in northeastern Ohio got off lightly from “Superstorm” Sandy, compared to places closer to the Atlantic seaboard and in the Caribbean. But still, over 250,000 people lost power due to high wind, especially in Cuyahoga and Lorain counties along the shores of Lake Erie, where huge waves also caused closure of an interstate and damage. Power crews are still working to restore power to tens of out thousands, and most schools and universities were closed for at least one day, if not longer.
There was also some rain. At my house, I got 4.25 inches (108 mm), which is almost exactly what the forecasts predicted. It came as both a drizzle and as heavy rains, but since last Friday afternoon we haven’t seen the sun. Now, northeastern Ohio is supposed to be quite cloudy, but given the local grumbling, this might be a bit of an extraordinary gray and damp cold run. It wasn’t warm rain either, with temperatures neither climbing out of the 40s F (8 C) or dipping below freezing. Isotopic results are pending, but my money is on our moisture source being almost entirely that northern airmass that got itself entangled with the tropical cyclone. Again, any whining about the damp is pretty well offset by everyone acknowledging that we are extremely lucky compared to states to our east.
All that cold rain brought the local river levels way up. There was major flooding on the Cuyahoga River at the downstream end by Wednesday, and the river at its upstream-most gage in Hiram crested on Thursday night. Flow at Hiram peaked around 1900 cubic feet per second (53.8 cubic m/s), which as I eyeball it on the USGS annual peakflow graph appears to be about a 2-year flood. This is actually consistent with my eyeballed estimate of the flow frequency produced by Sandy on Passage Creek, near Callan Bentley’s house in Virginia. I wonder whether that will be consistent for other rivers affected by Sandy.
For me, this was the first chance to the Cuyahoga River in action as it flows through Kent. The river sits in a gorge than separates the two halves of town, and that seems to keep the river from endangering much property in the town. But it did make for a pretty impressive roaring site and sound as I crossed the bridges today. Here are two pictures of Heritage Park in Kent on Friday afternoon about 4 pm. Contrast that with the low water pictures from early June.
If you live in the eastern 1/3 of the US and you haven’t started paying attention to Hurricane Sandy, today is THE day. This odd late-season storm is going to hit the northeastern and mid-Atlantic coast hard, having already stormed across the Caribbean, killing at least 48 people.
Much like we saw with Isaac earlier this year, the damage in slow-moving and relatively weak hurricanes (Sandy is a Category 1 currently) comes from all of the water in inland flooding and from the storm surge along the coast. When Sandy hits shore someplace between Delaware and New York City on Monday night, the storm surge is expected to be especially fearsome. As Ben Strauss at Climate Central explains:
- Sandy is projected to create tall storm surges, due to an enormous wind field influencing wide areas of ocean.
- The surge may be prolonged, due to the storm’s large size and slow movement. This means many areas will experience surge combined with at least one high tide.
- With a full moon near, tides are running high to begin with.
- Rivers swollen by significant rainfall may compound tides and surge locally.
- Sea level rise over the past century has raised the launch pad for storms and tides to begin with, by more than a foot across most of the Mid-Atlantic. Sinking land has driven part of this rise, but global warming, which melts glaciers and expands ocean water by heating it, appears to be the dominant factor across much of the region.
In Sandy’s path, as with Irene last year, lies the densely populated east coast. Which is why knowledgeable people are now talking about Sandy as likely to be a multi-billion dollar disaster. Jeff Masters of Weather Underground estimates that there could be as much as a billion dollars of wind damages and associated power losses, with flooding costing another billion in losses, and if the New York City transit system floods losses could run into the tens of billions.
And all of that is just the hurricane. Added on top of that is the potential convergence of the hurricane with a very deep upper-level trough over the central U.S. and unusually strong high-latitude blocking. Blocking occurs when a high pressure dome stays in the same place for several days or longer, blocking eastern flow of the polar jet stream, producing “seemingly endless stretches” of the same weather, and pushing storms far off their usual tracks. As explained by Will Komaromi of the Rosenstiel School of Marine and Atmospheric Science at the University of Miami:
“Normally a hurricane weakens as it moves northward, as it encounters an increasingly unfavorable environment. This means greater wind shear, drier air, and lower sea surface temperatures. However, with phasing [convergence] events, the tropical system merges with the mid-latitude system in such a way that baroclinic instability (arising from sharp air temperature/density gradients) and extremely divergent air at the upper-levels more than compensates for a decreasingly favorable environment for tropical systems.”
Komaromi goes on to explain that the Atlantic Gulf Stream is unusually warm for this time of year, allowing Sandy to remain stronger than it might have while out to see. Also, the extra strong blocking over the North Atlantic will mean that the hurricane moves very slowly and the storm will track farther west over the US rather than curving out to the mid-ocean. Komaromi shows that this is extremely similar to the 1991 “Perfect Storm”, subject of the book and movie of the same name.
The fallout of all this meteorological fury is likely to be felt both at the coast and far inland. The quantitative precipitation forecast for NOAA for the next five days shows eight states with areas expected to receive more than 4 inches (101 mm) of precipitation. Far more unusual than lots of rain is the possibility that Sandy will be a “snow-i-cane” dumping up to 12 inches (304 mm) of snow in the mountains of Virginia and West Virginia, and possibly into Tennessee and North Carolina. With leaves still on the trees in southern and coastal regions, the wind, rain, and snow will play havoc with above ground power lines. Widespread power outages are considered likely all the way into western Pennsylvania, New York, and West Virginia. Even in Ohio, my area is considered in the “possible” zone for power failures.
In addition to watching the weather and taking the necessary steps to prepare ourselves for whatever blows our way, a small group of scientists will be collecting precipitation samples for isotopic analyses by Gabe Bowen’s group at the University of Utah. If you live in the area affected by Sandy and want to help collect precipitation, look for more information here. I’ve already gotten 1.2 inches (30 mm) of rain since yesterday afternoon, and we’re not even seeing the storm effects yet. I’m likely to get another 4 inches (100 mm) by Thursday.
A somewhat larger group of geoscientists will be working on their posters and talks while hoping to avoid power outages and travel delays that could scuttle plans to attend the Geological Society of America meeting in Charlotte, North Carolina. Charlotte is not at all in the storm’s path, so if we can get there, everything should be fine.* I’m hopeful that the freeways will be open through West Virginia by Friday night, when I’ll drive south to convene two sessions, lead a field trip, and present a poster. But I worry for colleagues in the full brunt of the storm and hope that they have both adequate time to prepare for and attend the meeting. I’m also crossing my fingers that virtually all infrastructure is functioning again by Tuesday, November 6th, and that everyone affected by the storm will be able to cast their votes in a very important election.
As I contemplate coming events, I find the song “Storm Comin'” by The Wailing Jennys has been playing in my head almost constantly. I love how it captures the tension and anticipation of a storm rolling towards you across the plains or ocean.** Unfortunately, I wouldn’t recommend following this advice for emergency preparedness, instead you should take a make an emergency kit along the lines of this one and pay attention to watches, warnings, and evacuations in your area. Be safe everyone.
*Disclaimer here about being neither a meteorologist nor a disaster recovery expert, so don’t take my word as a guarantee. Also I’m glad I’m not in Italy.
**For me, music is poetry, so consider this my entry from the upcoming Accretionary Wedge carnvial on geo-poetry.
Cross-posted at Highly Allochthonous
Based on information from The Flood Observatory and other news sources, here are some tidbits about on-going and recent flood events around the world. Every one of these floods is having significant local and regional impacts, even if they don’t make the international news circuit. Common threads amongst these floods are the impact of the La Nina climate pattern and the unequal distribution of flood risks across the economic spectrum.
Cyclone Wilma hit the northern end of New Zealand’s North Island on Friday and Saturday 28-29 January, bringing with it intense rains, flooding, and landslides. Wilma unleashed about 28 cm of precipitation in just 12-14 hours, resulting in damage to homes, roads, and water and sewer treatment infrastructure. This was the fourth tropical low to impact New Zealand in just three weeks. The New Zealand Herald has a nice collection of reader-submitted images showing flooding and damage in various areas. My particular favorites are this flooded river valley and this road closed by a landslide. The New Zealand National Institute of Water and Atmospheric Research (NIWA) provides near real-time hydrologic, sea level, and climatic data through their Environmental Data Explorer, so I can show you quantitatively what this cyclone meant for a couple of rivers.
While the graphs above show discharge (flow volume per time), which is the unit of currency for hydrologists who want to compare multiple rivers to each other, local flooding impacts depend also on the depth(or stage) of the water. For reference, the Waitangi River goes from ~0.4 m before the storm to 6.2 m at the end of the record shown above. If you click through to this image on the New Zealand Herald website, you’ll see why the record for the Waitangi River ends when it does. That gaging station wasn’t meant for those flow conditions.
While Queensland begins to tally its losses and recover from massive flooding earlier this month, tropical cyclones aren’t about to make the job any easier. Cyclone Anthony brought mostly heavy winds to the Queensland coast south of Townsville Sunday night, and damage is reported to be minimal. But much bigger and much stronger Cyclone Yasi is expected to make landfall in the same area as a Category 4 storm later this week. This cyclone is expected to produce widespread, heavy rain, a strong storm surge along the coast, and winds up to 260 km per hour.
Meanwhile, in the southeastern state of Victoria, tributaries to the Murray River are also flooding. These floodwaters are still rising and are expected to take weeks to months to recede. Increasing my sympathy for the Australians, Victoria and South Australia are also experiencing a ridiculous heat wave, with temperatures reaching or exceeding 40 C for several days in a row.
Flooding occurred around the city of Jeddah over the weekend, killing at least 10 people. Three hours of rain produced 11 cm of precipitation, cars were washed away, and the video below shows the failure of a dam, which the videographer says contained a lake used for dumping untreated sewage.
Flooding in South Africa has gotten almost no international attention, despite the fact that floods have killed 120 people there and have caused disaster declarations in 8 of 9 provinces. Flooding has also affected Mozambique, where 13 people have died, and forecasts for continued heavy rains over the next several months have much of the southern part of the continent on alert. In some areas, up to 10 times as much rain as normal has fallen in the month of January. Tens of thousands of homes have been destroyed. Many of the lost homes are shacks belonging to poor Africans, because informal settlements are often located in low lying areas.
The clouds have cleared over the area around Rio that was hard-hit by floods and landsliding earlier this month. The death toll now exceeds 840 people, and the Brazilian federal and state governments have promised to provide up to 8000 homes for people that lost theirs in the disaster. The government also plans to immediately begin increasing its disaster preparedness, including mapping of high risk areas and better weather data collection. Dave Petley did a great analysis using before and after aerial imagery in one of the slide-affected area.
The USGS has released an interpolated precipitation map from the rain/flooding event brought on by Tropical Depression Fay last week. The worst flooding and damage occurred in northeastern Mecklenburg County in the region around UNCC and Cabarrus County in the towns of Concord and Harrisburg. No surprise that those areas are where the heaviest rainfall occurred.
While all eyes are already on Gustav (and for good reason), here in Charlotte we’re still drying out from heavy rains on August 26-27. Tropical Cyclone Fay made landfall in Florida a record four times and then wandered up towards the Carolinas from the Gulf Coast. In Mecklenburg Count (where Charlotte is located) and in Cabarrus County to our northeast, rainfall totals ranged from 5 inches to more than a food. According a USGS news release:
On August 26-27, twenty-four hour rainfall totals at 33 of 74 rain gauges operated by the USGS in Mecklenberg County exceeded the 100-year rainfall—50 of those gauges exceeded the 25-year rainfall.
While the rainfall totals were not recordbreaking, some of the flooding that resulted did set new records. Particularly affected were urban creeks in Charlotte, including Mallard Creek which flows along one edge of the UNCC campus and which has been the site of field trips for my Fluvial Processes class.
Here’s Mallard Creek at 2:30 pm local time on August 27th. This is about 4 hours after peak flow. Discharge at the gaging station downstream was 2900 cfs, down from a peakflow of over 6000 cfs. The peak stage at exceeded the previous maximum, set during a tropical storm, in 1995 by 2.1 feet.
Here’s a view of Mallard Creek a hundred meters from the last picture. I’m looking at a culvert outflow from the left bank. I’m standing on a bikepath which is serving as a levee and backing up floodplain water.
Here’s the same location on February 21, 2008 when I was teaching my fluvial processes students how to take discharge measurements. There was barely enough water to get a proper cross-section (Q<7.7 cfs). Obviously the angle is slightly different, but the rip-rap on the left bank is the location of the (then dry) culvert outflow).
Here’s a floodplain photo which I confess I did not take. However, my colleague Scott Hippensteel did manage to get some photos at around the time of peak flow. (I haven’t yet gotten a digital copy of the photo where he shows how the flood waters were within a few feet of the bottom of the bridge pictured above.) But do note that in the picture below one of the submerged signs warns that the trail is subject to flooding. That sign is probably 10 feet above the level of the submerged soccer fields. (You can’t even see the nets, some of which ended up at the downstream end of the field in a pile).
Finally, my sympathy to all those whose homes were damaged by the flooding. Something like 62 homes in Cabarrus County were damaged or destroyed and Charlotte-Mecklenburg Police had 39 calls for rescue or evacuation. One of the evacuees was a Watershed Hydrogeology lab graduate student Brock Freyer, who woke at 4 am to find six inches of water running through his rental house near Briar Creek. According to the USGS:
A flood peak of 16.09 feet was reported at Briar Creek above Colony Road (USGS Station Number 0214645022) at 10:00 yesterday, which exceeded the 1995 (15.6 feet) and 1997 (15.4 feet) peaks by about 0.5 feet.
However, I suspect that’s cold consolation.
All in all, it’s been an exciting week and we’ve learned some lessons about the immense amount of water than can be released by even stale tropical depressions, the effects of urbanization on flood peaks, and why you don’t buy or rent property in a floodplain.