| NJ is a state of many many rivers which flood badly enough that during the Japan Tsunami coverage on CNN, the anchor broke away for stories of flooding in NJ. We don't usually get 4 inches of rain in a day, but when we do, you can bet it will do some serious damage.
Even after all these years - NJ has had folks building here for 300 years already. Why do we still have such a hard time dealing with those little drops that fall from the sky?
Having worked in the field of stormwater management for 11 years I think I can tell you why. The reasons are not only scientific, but political, and very much dependent on human behavior, ego, stubbornness and fear.
Let's start with the scientific. Rain falling on a virgin piece of forest causes actually very little runoff. The rain hits each leaf, each branch, coating it first. A little splashes into tiny drops that evaporate quickly. This is why a tree is looked at by a stormwater engineer as a giant sponge in the air. Then the water makes its way slowly down the tree. Have you ever stood beneath a tree during a storm? You usually get a good few minutes of dryness - because the tree has intercepted quite a bit.
Then that water makes its way down the trees leaves dripping ultimately to the forest floor, where a mound of rich vegetation slows it down even more. It slowly seeps downward and much more gets absorbed by the decaying underbrush, and then, because the ground is pervious through the action of worms and critters in the fertile earth, the water that is left - that hasn't coated the trees and bushes or been locked in leaf litter or the soil, starts to move. It moves downward under the topsoil through cracks in the bedrock to underground aquifers. And also - this is important - it also moves LATERALLY - sideways to the nearest waterway stream or brook, OR low spot. It is water after all. Gravity affects it, but so does pressure, and osmosis. It will move wherever it can - except up (without a pump of course).
On a virgin piece of forest, there is practically no runoff at all. But here in NJ, where we LOVE our new construction, we see it all the time. ANY time you destroy virgin forest, you WILL create runoff. The tree is no longer there to intercept the rain, so you increase the water that reaches the earth. When you clear natural forest brush and replace it with lawn - which can't hold as much water, you increase the water even more. The soil can only hold so much water and can only pass through so much at a time - it's percolation rate. The overwhelming of the ability of the water to slowly seep to rivers and streams and aquifers means it's got to go somewhere, and so it becomes runoff - the stormwater you see. The water starts out as what we call sheet flow. It is like a very thin layer on a lawn, flowing down a gentle hill. After a certain distance, that water teams up with more water from the sky, and pretty soon, you have a rivulet, eroding the soil and making a sort of channel. These gullys concentrate the water further and pretty soon, you have even more runoff, which if you have ever had problems with this - and if you live in NJ you have - you can't grow anything in your yard because the topsoil has soon washed away. If you live near a river that is also now taking runoff from a thousand little runoff sources, your life may actually be in danger from the force of floodwaters exceeding the banks.
Now, that's just cutting down forest and replacing it with lawn. When we calculate runoff, the coefficient for forest is .25 - meaning the forest intercepts about 75% of the stuff that just fell from the sky. The coefficient for lawn is .51 - meaning the lawn now only intercepts HALF what the forest did. You just increased flooding potential without even BUILDING anything yet.
Now, when you slap a patch of concrete, or asphalt, or a building down over soil that used to absorb water and held it temporarily and kept it near the surface available for plants to use and return to the sky in a process called evapotranspiration, you now eliminate the soil, and the plants' contribution to avoiding runoff. You have pretty much just created runoff from nearly ALL the rainwater hitting the earth. And if you calculate it often, like I do, you start to realize just HOW MUCH water that is.
The quick and dirty formula is just this: CIA
C is the coefficient I just gave you. I is the intensity in inches per hour. Engineers typically use 2 inches per hour to size something to hold stormwater off your roof - for example. A is simply the area in acres. That gives you the amount of rainfall in cubic feet per SECOND. Multiply that by duration of the storm, and you get the volume.
On a typical 8th of an acre - a 5000 sf lot - completely covered in asphalt - the amount of stormwater runoff is 0.2 cubic feet per second. That doesn't seem like a lot until you add up all those seconds in a one hour. It's over 720 cubic FEET for just a one hour storm. 720 cubic feet of stormwater from just one property - that has to go SOMEWHERE. Add up all the properties in even a suburban neighborhood and you can see why we are in this mess.
Well, where do we put it now? Good question. For many many years stormwater management consisted of just getting the water as quickly to the river as we could. Move it away from where it fell. That is where the phrase "God willin' and the creek don't rise" came from. When we sent our water away, we found out it actually killed folks living along the river because the river would reach dangerous flood heights we never realized it could.
Then we realized, we had to slow it down on its way to the river, so we came up with the idea of just putting it into a pond or underground temporary storage chamber to slow it down before it gets to the municipal stormwater system (detention) or sticking it the ground in what we call seepage pits (retention). One of the very first things they teach you in engineering school is how to calculate the rate of flow out of a pond. But in NJ space is at a huge premium so we prefer the underground tanks or seepage pits - big round manhole type things we stick in the ground that have holes in them to let the water slowly seep into the aquifers again. We were so darn proud of that achievement. Out of sight, out of mind. However, we now know of a phenomenon called "mounding". We are still dealing with MORE volume than before. When we put water into the ground quickly, it raises the groundwater level and homes that never used to flood ON HILLS yet in places like Wayne and Tenafly, now regularly see flooding in their basements. The water will seek its own way, and if that low spot is your basement - well, so be it. The water goes where it wants to and wherever it can. When we started to build on mountains and tore down heavily wooded areas, we practically invited the water into our basements.
In Englewood Cliffs, where the Palisades bedrock is just a few inches down, the mansion builders after cutting down many many trees, had to blast a hole in the rock to put the oversized basements with the home theaters in. To meet the building height requirements, they had to dig down. Now we have essentially homes sitting on top of bowls in the Palisades rock with sunken garages and places water just LOVES to collect. And we wonder why the basements in Englewood Cliffs flood even though they have seepage pits in the yard. It is also why they now are trying the newer techniques in Englewood Cliffs now because the old ones have so spectacularly failed.
Municipalities are still under the impression that a seepage pit will correct a lot of environmental abuse. It won't. Because it isn't just collecting in basements. It moves laterally, remember? If you send a bunch of water underground faster than the ground can recharge the aquifers or percolate down, it WILL pop up above ground further downhill. It just likes to do that. Like a mountain spring. Which is why we are now seeing flood damage on the TOP of the cliffs and sometimes devastating rivers of water cascading through some NJ gardens and backyards seeking a lower level. I saw MORE flood damage when I was a Councilwoman in Tenafly on the TOP of the cliffs, than I did near the Tenakill. By putting that water below the root zone in a seepage pit, you are also not using the process of evapotranspiration. Plants DRINK rainwater when they can reach it. By just putting it deep - you are putting it out of reach of plants that could get rid of some of that for you.
The flooding happens now because the older towns just don't have the infrastructure to deal with the increase in flow. The pockets of wooded open space hid a lot of sins for us. Instead of letting the streams breathe, we for some reason didn't like bridges and thought we could tame nature. So in our dam-building fervor, we also tried to squish any waterway through a corrugated metal pipe, and slap asphalt over it so we could save on building a bridge. By doing that, we limited the capacity that any waterway could handle.
In many parts of the country, the effort now is to remove dams and culverts and open up waterways so that they can expand when we need them to accommodate floodwater. But here in NJ, we have so many pipes and culverts designed for an earlier age of less pavement and more woods we regularly overwhelm our infrastructure. In some places we still have the stormwater sent through the same pipes as the raw sewage, which is why the sewage system gets overwhelmed during a storm. In some places where the stormwater and sewage lines are separate, the infrastructure is so old that stormwater seeps into broken sewage pipes anyway and increases the load on our treatment facilities - and also the cost.
The main problem as I see it is trying to do things the old way. Because that is how we always did it and the engineers (as Lionel would say) "God bless their hearts" who built all these things that no longer work are still around and doing things the way they were taught 60 years ago. This is where the ego and stubbornness come in.
The realization and the really hard work of trying to reverse the sins of the past only happened within the last 20 years, but many of the engineers who were trained long long before that refuse to be retrained. They are advising our Municipal elected officials and advising them poorly.
Around the same time we started to see the real impacts of overbuilding and environmental abuse, environmentalists realized that pollution wasn't just coming from a pipe out of some factory, and that stormwater erosion didn't just erode topsoil and cause the Dust Bowl of the 30's. Soil erosion carries POLLUTION along for the ride on each tiny grain. By trapping the stormwater where it was and treating it right there, we could protect our waterways from "non-point source pollution". There was now an even nobler reason to address runoff other than flood and erosion prevention - pollution prevention.
For all the vilifying of public employees and the NJDEP, I have to give them a lot of credit. They have discovered long ago that the old ways just don't work in the New Normal of climate change and overdevelopment. They have been struggling to correct the problems I have just recounted for you. However, they are getting very little help from the older engineers and elected NJ officials.
The NJDEP is on the right track in terms of the science. They are working closely with the folks breaking new ground in stormwater management. The new way forward is Low Impact Development, which is using nature - soil and vegetation to try to mimic nature's way of preventing runoff in the first place. The NJDEP and folks there like Sandy Blick have been working hard to bring this knowledge to engineers in the state. They regularly hold classes at Rutgers on this topic. But I RARELY see Municipal engineers there learning the new techniques when I attend these great classes. Which explains why when I design using these new techniques endorsed and encouraged by the NJDEP, I am forced to UNDESIGN them and go back to using the old pipe and concrete everywhere methods that the Municipal engineers feel comfortable with. They are afraid of doing something new once they know all the ways to calculate things the old way. That is where the Fear comes in. It is absurd and backwards, and all kinds of frustrating. And NJ gets wetter.
So, there you have the Science, the Stubbornness, the Ego and the Fear reasons. Here are the political ones:
Mayors. Mayors get to determine what gets built in a town. EVERY member of a planning board is appointed by the Mayor except ONE who is chosen by the Council. Mayors also appoint the engineering firms for a municipality. Too often they do it based on Pay to Play and how much that engineering firm - like Maser or T &M donated to the BCDO or some other Party Boss's coffers. THAT can not only cost you much more, but can result in more runoff. One ignorant Mayor can do a lot of damage. They can sway a Board with the threat of not reappointing a member or Planning Board engineer who disagrees with them. They can do a lot of damage by fast tracking large projects of major donors without a thought of how overdevelopment can cause flooding. That is only one way. The most common one and not malicious is just not understanding what causes flooding. For example - thinking that lawns are REQUIRED just 'cause they look nice. I recently worked on a project in the town where the Mayor demanded that the entire front of all properties in the subdivision had to be lawn. This tremendously large town is one of the towns that CNN broke their Tsunami story to talk about flooding in.
I was NOT allowed to use pervious paver sidewalk. I was not allowed to use pervious pavement for the road. They DEMANDED the impervious roadway be 50 wide right of way even though it only served 3 single family homes. They wanted impervious concrete sidewalk on BOTH sides of the road even though it would cause us to lose many more trees. They just passed law requiring impervious asphalt for driveways, and denying the use of pervious pavers for driveways. They refused the use of bio-infiltration for treating the roadway runoff, and the rain gardens I had there to treat roof runoff had to go bye bye too. As a final insult, I had to fill out the non-structural point system spreadsheet put out by the NJDEP to show I was using the techniques the town told me I was actually, ridiculously, FORBIDDEN to use.
It was the first time I ever, ever, showed my emotions in front of a Planning Board. The Mayor blew up when we mentioned the term "impervious surface". When we said we wanted to limit the amount of pavement because of impervious cover, he yelled that we only wanted to save money on pavement. The politics of not wanting to tick off an ignorant Mayor so you can get an approval causes a lot more runoff than you can ever imagine. If Contractors knew they could save a lot of money by using plants incorporated into the landscaping instead of concrete pipe and ever larger underground boxes or unsightly huge detention basins (these are passé too) to detain the ever increasing runoff, they would do it in a heartbeat. The fact that they are NOT ALLOWED to use these new (and aesthetic) cutting edge techniques at the Municipal level while these same techniques are encouraged at the State level is enough to give any design engineer agida. It is also enough to cause more runoff.
What to do? Fortunately, there are some municipal engineering firms who understand LID techniques and what the NJDEP has been trying to accomplish. Some happen to have hydrology experts on staff who actually know what a rain garden is. Even homeowners are more knowledgeable about rain gardens, green building techniques, and rainwater recapture than most of our municipal engineers. I would recommend Municipalities DEMAND any municipal engineer have an expert who knows LID techniques and will actually encourage their use. Someone who will be REQUIRED to attend the yearly seminars by the NJDEP that teach the latest LID techniques. They should also require every Planning Board Member take a one day course in LID techniques as well. We need to look at stormwater as a regional issue and a "fluid" one. The science on this is coming fast and furious and we need to keep up. For too many years NJ licensed engineers were not required to earn continuing education credits to keep their licenses. Now they are. Let's hope that leads to me running into more municipal engineers at stormwater class. I've missed them.
I am encouraged that NJ has created a new Commission on Flooding. Mother Nature isn't the problem, we can withstand what she throws at us but only if we address the human and political issues first. I hope the new Commission seriously lends a hand to the NJDEP who has been trying to champion new stormwater techniques for years now to no avail.
There are many many ways of dealing with stormwater even in our crowded NJ towns. You would be amazed where we can put bio-infiltration strips. Existing parking lots can be retrofitted . Existing catch basins can be retrofitted. Flow though planter boxes around city buildings. Green roofs. We can fix the problem, what we need is the political will to do it. New municipal projects should be models for residents to see these things in action that can be done on individual properties. What we need is a regional approach and individual action. The whole think globally act locally mantra works on stormwater. A tiny rivulet is much easier to deal with than a raging river.
We all know what happened to the dinosaurs. They couldn't adapt to the changes in their environment, we don't want the same thing to happen to us. |
.gif)
