Stormwater, the early years (7/10/2023)

In a previous post I mentioned that I once had the ambition to write a book on stormwater and erosion and sediment control (and I may still do it). This idea was a natural outflow of the job I did pre-retirement. The following post is part of an introductory section that I wrote for the book. Ince I lifted from a chapter, I have changed it a little to make it a narrative for you all to follow and understand. I left the literature citations out, feel free to contact me, if you are interested in them. So here I go:

Very early, North American settlement history may have followed similar patterns as were encountered in Europe of the Middle Ages. The settling population in North America initially concentrated in towns and villages for mutual protection from outlaws and native Indian population. This is evident by some of the older larger urban centers on the east coast. In addition, large tracts of land were deforested very early on in settlement history for the use of timber (building materials) and the growth of cash crops, in particular tobacco. A 17th century document in the historic town of Williamsburg describes that climbers of the church spire in town (or what is now Colonial Williamsburg) were able to see the York River to the north and the James River to the south, a feat that is impossible nowadays because of the regrowth of the forest in the area. The peninsula appeared to have completely deforested, mostly for the growing of tobacco at that time.

The cartographer Lewis Evans observed the same thing when he reported in 1750 about the deforestation and conversion to agriculture land that had already greatly altered the hydrology and clarity of streams and creeks in the Piedmont of Northern Virginia:

"When the country was cover'd with Woods, and the Swamps with brush, the rain that fell was detained by these interruptions, and so had time to insinuate into the Earth, and contribute to the springs and runs. But now the country is clear'd, the rain as fast as it falls is hurried into the rivers, and washes away the earth and soil of our Naked Fields."

 

The reports by Evans were only the beginning. Human caused accelerated erosion increased steadily as is shown in a recent study by Kemp et al (2020) who conclude that European settlement of North America during the past century has resulted in the movement in as much sediment that natural processes can move in 700 to 3000 years. They estimated that geologic sediment production which had been relatively stable for the past 40,000 years increased 10-fold as a result of European settlement and the rapid expansion of agriculture and river modification seen throughout the continent.

So, what are currently the main sources of sediment the waterways in more developed nations? It was reported that while agriculture practices generate considerable amounts of sediment by way of erosion; we now estimate that areas cleared for construction are able to generate the equivalent of many decades of sediment in one year compared to agricultural uses (let me know if you are interested in the source). Research determined that construction can yield 140,000 tons of sediment per square mile per year, compared to 1000 tons from agriculture land and up to 500 tons from forested land in the Piedmont area of Maryland. In other words, construction is a major contributor producing 140 times more sediment than agriculture land per unit area (for example per acre or hectare). However, , there is so much more land being used for agriculture than actively being disturbed by construction activities.

On an interesting note, while sediment production increased at least 10-fold over historical times in North America during the last century, it was also observed that during the same period it seemed that less sediment reached the ocean. This was caused by the retention of the sediment by reservoirs that were constructed by human. Reservoirs served for the storage of drinking water and water for energy generation and irrigation. It has been estimated that a total of 1.4 ± 0.3 metric tons of sediment per year is retained by reservoirs world-wide. Siltation of these reservoirs will eventually greatly reduce the capacity, function, and usefulness of these structures. It appears that Indonesian rivers were a rare exception and that they deliver more sediment to the coastal areas than other rivers that they surveyed.

Here I’ll step away from my book chapter. I saw similar issues in Nepal where the land or better fertile soil was being carried away by runoff. The main reason was deforestation for agriculture. We often joked that a new island was being formed off the coast of Bangladesh. This island was formed from the sediment being carried by the rivers coming out of Nepal. The results in Nepal were the drying out of springs and dropping groundwater table, a phenomenon seen throughout areas that are being deforested.

I’ll end here, there are many posts where I discuss some of these items as well. Just look in the keywords for the words like stormwater, erosion, sediment, erosion and sediment control, runoff reduction and alike. If you like or enjoy what I wrote here, let me know and I’ll pull some additional material out of my writing.

Our daughter was in New Delhi, India these past few weeks and sent me this newspaper shot.  They had 6" (126 mm) of rain in the afternoon and it flooded the town.  Can you imagine all the impervious area in such a large city, it created havoc.

Stormwater (11/1/2015)

I have been doing some literature research on the history of stormwater management.  OK, call me a stormwater geek or a stormwater nerd, but I just realized that I have been actually fascinated about it for probably more more than forty years and I never noticed it until this weekend.

It all started in 1972 when I read an article somewhere about an agriculture and reforestation project in the arid mountains of Algeria.  This fascinated me and prompted me to do a literature search on the subject of desert revegetation at my college library in Holland where I found a reference to a new (scientific) book by Michael Evenari and co-authors called: The Negev, The Challenge of a Desert.  It was published in 1971 and I borrowed it through inter-library loan.  It came from the Dutch Library of Congress, it appeared that I was the first one to read it.  I devoured the book.

In this book Evenari and his colleagues describe how the old Bedouin tribes were able not only to survive in the desert but actually to thrive by practicing agriculture in the Negev Desert of what is now Israel.  They built extensive drainage canal systems on hillsides that captured runoff from the sparse winter rainstorms and brought the water down to the agriculture fields.  Very different from what we did with stormwater until the early 2000s; which is, getting rid of it.  At least now we are back to teaching people to conserve stormwater; to conserve it and infiltrate it.

Walking to work in Richmond this morning (11/3/2015), ready to go back out on the road and teach about stormwater management and conservation, and erosion and sediment control. 

I have always credited Evenari for steering me into the field of desert ecology; his book has a chapter on plant survival in the desert environment and it was my first encounter with that subject as well.  Ever since reading that chapter I have been fascinated with plant physiological ecology, in particular the adaptation of plants to stressful environments such as deserts, the subject I specialized in for my PhD.

Events in real life kept reminding me of Evenari's book.  In Yemen I saw some of the same water harvesting practices that he described seeing in the Negev Desert.  I also saw the same plant adaptations in Yemen and in New Mexico as he saw, and it always brought me back to his book.  So much so, that  Evenari's book was one of the first purchases I made on the fledgling Amazon.com years ago, it was a book that always stayed with me.  So yes, it was fun to open it again this weekend and to leaf through it again.

Now 40 year or more later I can credit Evenari for even more than just turning me into an physiological ecologist.  Truth be known, I am more a stormwater geek or nerd now; maybe also thanks to that book, a realization I all the sudden have all out of the blue.  It is fun to see how your life comes full circle, all the way back to stormwater management, the most important subject in the book.  It is amazing how one event, or one book can have such a (subconscious) influence even if you don't realize it then, but only now 40+ years later.  I am sure that many of you have events, books or even radio or television shows that are somehow pivotal to your career or even your life, that you do not realize until many years later.  Cherish those moments, I cherish mine right now.

Stormwater Management (12/21/2014)

What, no location on this post?  My back yard, Yorktown or even Newport News Park would be a decent heading as well, but this post is more than that.  It speaks more to one of the things I like to do (landscaping, architecture, building, paving) and things I teach (stormwater management).

Over the past two weekends we decided that a strip of grass between two paved areas in our back yard was more of a bother than an asset.  The few things it was good for was that it had some clover (good for bees) that sometimes did reasonably well early on in the year, and that it is the area that receives the overflow from one of our rain barrels and thus serves as an infiltration area for water coming of our roof.

That water infiltrates into the soil is a very important thing to me.  I give impassioned talks about this subject in the classes that I teach and talks that I give throughout the state, in particular since we are definitively seeing a drastic drop in groundwater tables in areas that are developed.  Areas that are turned into subdivisions and shopping areas become less pervious to rainwater than the forested area or agriculture land they were before development.  Rain falls onto impervious surfaces (roofs, roads, parking lots, etc) after which it enters some form of stormwater management system and is piped into the nearest stream or river.  As a result, rainwater that used in infiltrate and recharge our groundwater tables now runs down ditches into a river and out to the sea, or in our case the Chesapeake Bay.  All this added water in the streams also causes flooding downstream and more erosion in the streams during rainstorms while in dry periods the streams are drier than they used to be.  In essence, building subdivisions is not the best for our natural environment; although it is a necessary thing to do; we need to live too.  But I believe in sensible development and less urban sprawl (search my blog for the label urban sprawl and you'll see what I mean).

What I teach is also known as Low Impact Development.  Yes, we need homes and subdivisions, but we can build them sensibly, with respect for our natural environment and for the ground water resources.  When we do that we alse take care of the water quality and quantity in our creeks, rivers and streams.  Instead of piping the water away, we need to help it infiltrate with things like rain gardens, bioretention permeable pavement and other measures.  That was what I was looking at when doing my paving job. 

In this job, I used all kinds of recycled materials.  When we lived in Cincinnati my wife and I would even clean up the Ohio River and pick up old brick that were dumped along the river.  In this job, the tiles were from a walk way we took out and the brick are all recycled from old building projects (my wife and I spent long hours chipping away the cement that clung to some of these brick). 

Giving the brick and tile a bit of a grout line will help with some water infiltration; but we had to deal with the overflow from our rain barrel.  Luckily we had what I call holy brick, or brick that is uses as veneer to a home.  These brick all seem to have three holes in them (hence the holy in holy brick).  So we constructed a slightly depressed channel of these holy brick between the tiles.  We routed the water from our rain barrel through this channel in the hope (expectation) that any overflow will infiltrate through these holes into the soil; thus achieving what I teach: runoff reduction.  We will have to monitor it and see how it works.  The photo below show the results of a two-weekend job, minus the sore back.