flooding issues

City Says "No" to Development Because of Flood Risk - First of a Kind!

 Road Near Proposed Development - Virginian Pilot/Ron Stubbins photo

Road Near Proposed Development - Virginian Pilot/Ron Stubbins photo

For the first time that we can find, a local government has said "no" to a development proposal due to flood risk. The City of Virginia Beach, hammered by increasing rainfall, has been more sensitive to the flooding potential, especially in the low-lying southern part of the City. But lots of localities are concerned about and planning for flooding, but still allow people to develop in dangerous places.

No more in Virginia Beach. The City Council unanimously denied a proposed 23-home subdivision on a soggy piece of land because of concerns about flood risk and future city liability. Recently burned by the flooding in a recently constructed subdivision, Ashville Park, Virginia Beach Planning Commission and City Council members expressed doubts about this proposal. Even though it met the technical requirements, the access roads flood frequently, flooding will increase, and the city did not want to put more people in harm's way.

This follows on the City's work to document the increased rain flooding risk that is equally important and groundbreaking.

Stay tuned for lawsuits and negotiations, but for now the City of Virginia Beach is the first in the country to say "no" to soggy development proposals.

Study Confirms What We Are Seeing - Nuisance Flooding is Increasing/Will Continue to Increase

 Porjections of flood days per year, from NOAA Study

Porjections of flood days per year, from NOAA Study

SNAPSHOT: A new study from NOAA projects increases in high tide flooding onto streets and sidewalks in shoreline communities. These floods will occur every other day - possibly every day - by 2100 even using very conservative sea level rise estimates. Given the time and money required to mitigate the damage from this constant flooding, we need to start yesterday to put adaptation measures in place.

BACKSTORY: Anecdotally, Wetlands Watch has been hearing for years that tidal water levels seem to be increasing. At community meetings and service club talks, we heard more complaints that tidal waters were lapping over roads and sidewalks and coming up out of stormwater pipes and ditches. We observed changes in rural ditches in Mathews County, ditches that were dry when we started working up there in 2008 and now are full of water most days and have tidal wetlands plants growing in them. We have documented this nuisance flooding in urban areas.

 Projections for Downtown Norfolk, VA by Dr's. Tal Ezer and Larry Atkinson of Old Dominion University.

Projections for Downtown Norfolk, VA by Dr's. Tal Ezer and Larry Atkinson of Old Dominion University.

In the graph above, two oceanographers from Old Dominion University in Virginia developed projections of future nuisance flood risk. The blue in the graph is the observed flooding (hours per year) since the tide gauge at the Norfolk Naval Station was put into service in 1927. The green bars in the graph are the projected flooding hours/year with the current rate of sea level rise. The red bars are the projected flooding hours/year with the accelerated rate of sea level rise we are seeing, about twice the current rate.

Solutions? Start today with detailed maps of where flooding will occur. Take extra precautions to build "freeboard" or additional flood protection into local land use actions or federal investments along the coast. Start developing comprehensive plans among all the stakeholders - public and private - to address the flooding.

Oh, and we need to start stacking up the dollar bills needed to pay for all the work we have to do.

What Makes Up "King Tide" Flooding in Hampton Roads?

perigean.jpg

The "King Tides" that we will map on November 5, 2017, are correctly called "Perigean-Spring Tides." These are the highest predicted tides of the year given the alignment of the moon, earth, and sun and happen with the fall full/new moons in SE Virginia (highest at least on paper - but more on that in a minute). We can predict these tides years ahead...as shown in the chart below.

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The tide chart shows our region's normal cycle of two high tides and two low tides a day. And each month we get higher high tides on the full and new moon, also called "spring tides," when the celestial bodies align as shown in the first picture above. However in the fall of each year are the yearly tide cycles that produce the "King Tides," when the celestial alignment occurs and the moon is closest to the earth - at Perigee.

The chart shows a relatively normal high tide in the red circle to the right and the highest perigean tide of the year on our target King Tide mapping day, November 5, in the circle on the left. The numbers are the height of the water above Mean Lower Low Water and, in the example above, the November 5 tide will in theory run about 10 inches higher than normal. With no wind, this would cause minor flooding in the lowest lying parts of our region.

But in our region, the wind plays a major part in our water levels, in addition to the daily, monthly, and yearly tides. Without going into too much geeky detail, we have a very rare shoreline with rivers that run south-to-north. [That shoreline is the southern rim of the largest meteor impact crater in the US, a big bang that happened 56 million years ago!) And these rivers are not white-water rivers with a lot of downhill flow - they are flat estuaries with flows that winds can push around. So, when we get a wind from the north, blowing into the mouths of the rivers, the water starts stacking up. Conversely, when we get a wind from the south, the water flows out into the Chesapeake Bay and our flooding is minimal (though with a south wind Back Bay will start flooding but that is another story).

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This means that on top of the daily, monthly, and yearly tide cycles we have to figure in the wind. Here's an example of how that works. In this Weather Underground screen shot from last October look at the line of arrows at the bottom, showing the wind speed and direction.

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Starting on October 8 (red circle), the wind shifted out of the N/NE at 20+ miles per hour and started pushing water upstream on our slow-flowing, north facing rivers. Even worse, it kept going for the next few days. This started to cause flooding - as shown in the chart below from the tide gauge at Sewells Point at Naval Station Norfolk. By high tide on the second morning, the tide was 4 feet above mean sea level.

projected-tides.jpg

To paraphrase Burt in "Mary Poppins":

"Winds in the [nor]east, mist coming in, / Like somethin' is brewin' and bout to begin. / Can't put me finger on what lies in store, / But I fear what's to happen all happened before. "

Sure enough, this wind from the nor'east produced nuisance flooding across the region. In Norfolk, it looked like this on October 9.

 Colonial Place gets wet (again) on Oct 9 on a sunny day.

Colonial Place gets wet (again) on Oct 9 on a sunny day.

Now we've also got the rain to figure in but we talked about that before.

Right now, for our Nov 5, 2017, King Tide Event, the wind looks to be shifting to the N/NE, meaning we'll probably have some water to measure, although we hope not as much as in the picture above.

Fall Storms Bring Flooding to SE Virginia

The impact of four feet of flooding on Hampton Boulevard, the major N/S road in west Norfolk. This is one of two roads leading Naval Station Norfok.

Jose and Maria are messing with Southeast Virginia. The video above is Hampton Boulevard in Norfolk, VA during the run up to the high tides on September 19, 2017, from Jose. On Sept 26 and 27 another set of high tides is hitting. At least these "modest" floods help us find all the areas that flood so we can put them on the map.

We are also in the midst of a major regional, crowdsource flood mapping effort around the hugest projected tide on November 5, 2017, the so-called "King Tide" of the year. We've been holding mapping trainings leading up to that event.

During the Jose floods I was out in the water doing some mapping. The images below show a flooded residential neighborhood in Norfolk (left) and the flood mapping I did (right) using the Sea Level Rise phone app. Walking the edge of the flooded zone, I dropped GIS pins every 4-5 feet and got an outline of the flooding., showing the extent of the inundation. The data set can be exported as an .xls or .csv file and transformed into a shape form on a map and used to test inundation models. All of this helps us project where the water will come next time we get +4' of water.

Vehicle Flood Loss Needs a Strategy

 October 2, 2015 Nor'easter Catches Norfolk Motorist

October 2, 2015 Nor'easter Catches Norfolk Motorist

Nearly all the talk on flooding and mitigation involves real estate and property damage. Very rarely is the issue of vehicle damage and loss discussed in flood mitigation planning. Much of that is because there is are federal, state, and local programs dealing with real property flood losses. To be eligible for the federal government National Flood Insurance Program a locality has to have flood plain plans, ordinances, etc. but they mostly deal with real estate protection. Vehicles are privately insured so there is no requirement to develop comprehensive plans to prevent auto losses. However, Hurricane Harvey is showing the extent of those losses, highlighting the need to start dealing with them.

Vehicle losses are largely preventable because, unlike houses, you can move your car to higher ground - or the elevated public garages that most cities open as flood events approach. As long as you don't drive onto flooded sections of road - like the car above - you can protect your car.

Preventing vehicle loss, however, is more complicated and expensive than real estate flood protection. Road inundation information is not comprehensively reported nor is location of auto losses. (We are trying to deal with the road inundation mapping with our smart phone app.)

Elevating low-lying sections of road is expensive and paying for the work falls mostly on state and local government transportation budgets. There is no dedicated transportation flooding adaptation funding anywhere at the state or federal level, so this work competes with regular transportation maintenance projects. Federal funding to address these needs comes AFTER a flood event in the form of disaster relief.

The city of Norfolk, VA spent $1.2 million in 2010 raising one block to fix the flooding in one residential neighborhood. It spent $2.4 million raising a 200 yard stretch of a major downtown road 2 1/2 feet to prevent flooding. Luckily Norfolk has a plan, so that these projects fit into their larger adaptation puzzle. But no city has a comprehensive way of addressing vehicle losses due to flooding.

Auto flood losses are more widespread than house and business flooding, with nearly 50 % of households reporting flood loss citing auto damage/loss, according to a recent study done in Portsmouth, VA. And insurance companies are starting to notice. Just an anecdote but I recently heard from a person whose auto insurance company refused her renewal because her street address showed too many surrounding auto flood losses.

If we're going to get a handle on adaptation costs and needs, we need to start dealing with the auto damage and loss piece of the puzzle.

Sunny Day Flooding - More and More of it

On July 30, 2017, we had a high tide caused by wind from the N/NE. The wind pushed the water about 4.5 feet above mean sea level and unfortunately that is all it takes here in Norfolk, on low-lying streets, to cause flooding. The stretch of road in the video below is Llewellyn Ave. It is known to flood all the time, such frequent flooding that the city has installed "rulers" alongside the road to let you know how deep the water is. Such frequent flooding that the plants in the foreground are wetlands plants.

This was a wetland 100 years ago, was filled in, and now it wants to be - is actually becoming - a wetland again. No wonder when we ask people at public meetings, "How many of you have driven through salt water on the roads in the last year?", most of the hands go up.

The pictures below were taken that same sunny day as I wandered around the city of Norfolk to record the nuisance flooding these events bring. Again, not storms, just wind at the wrong time of the tide cycle...and we get water running onto the street

Climate Change = Intense Rain = More Pollution

Yesterday (July 18, 2017) we had one of those intense rain events we're seeing with increased frequency. My rooftop rain gauge measured 1.8" of rain in two hours. I was out picking up my daughter at track practice when it hit and got stranded - see windshield shot as I was stopped in a flooded intersection. Last week we had another ~2" rain event.

This morning walking my dog, there was sediment in the streets everywhere. It washed into the Elizabeth and Lafayette Rivers here in Norfolk and was like dumping bags of fertilizer into the rivers. My wife, Dr. Margaret Mulholland, is a biological oceanographer studying algal blooms and she said they are already seeing harmful algal blooms due to last week's deluge...yesterday's "rain bomb" will only add to it.

So going forward we need to add climate change/rain intensity to our stormwater management plans. We get ~60" of rain a year here in Norfolk. If we get 120, 1/2" rain events, no problem, the existing stormwater management systems can handle it. We get 30, 2" rain events, the pollution wins.

This increasing intensity was studied by Peter Popmmerenk who is a planner with the City of Virginia Beach's Stormwater Department. He went to the weather record at Norfolk International Airport and...sure enough, he found an increase in 2" rain events since 1950....measured, not projected from someone's model. The relevant diagram is below - click on the image for his full paper.

 

Just another part of the challenge with flooding/stormwater.