A Call for Permeable Paving

with permeable paving, stormwater doesn't all become surface runoff
With permeable paving, all stormwater doesn’t become surface runoff
Image Source: Flickr

I’ve said it before and I’ll say it again: urban dwellers have an obsession with paving every possible open space.

Housing society compound?
Pave it — we need to park our cars!

Open area where social interactions take place?
Pave it — our clothes get muddy!

Barely-used internal road?
Pave it — we get stuck in the monsoon and it’s hell on the tyres!

If we Must Pave, Let it be Permeable

Some of this paving may well be justified but, because it is done indiscriminately, it leads to a boatload of problems related to the water table, the health of the city’s trees and even the heat we’re subjected to. I’ve written all this in greater detail elsewhere on this site but this particular post is about a type of product that could help in such situations.

In late 2015, there was a buzz in the construction world as Lafarge UK showcased a super-porous asphalt that could guzzle an incredible 4000 litres of water in about a minute. Media started calling it “thirsty concrete” and truly, if you watch the video below, it does look like the water is vanishing into desert sands.

Permeable Concrete Video

I have never been a great fan of the wasteful use of concrete but, when it is required, the least we can do as architects is to try and use it correctly.  Unfortunately, at least as far as I can tell, this product and others like it are not readily available in India. In fact the only case I know of permeable concrete being used, is for a parking lot at Jaipur railway station.

Unless architects and engineers specify such products and create a market for them, there is no way that companies will manufacture them here. I do hope some of my brethren in the industry take up the call.

Reduce Hard Paving

In our urban environment we see numerous examples of open spaces with hard paving all over them. One of the reasons for this is our insatiable hunger for parking. The earth in our cities is starved of air and water — sacrificed at the altar of our rubber-shod tin cans.

“Ah”, but I hear you say, “we really do need that parking space!”.

Of course, if our city fathers were more enlightened and aimed for better public transportation instead of caving in to the cult of the car, we wouldn’t have reached this impasse in the first place. However, this page is not a rant about ineffective urban planning but about the effects of indiscriminate paving and what we can do about it.

When we pave over open spaces, a number of things happen.

The Water Table Drops Dramatically

This one is pretty obvious and hardly needs an explanation. If the ground is paved, there is no way that any more than a tiny fraction of rainwater will ever reach the soil. In Bombay, there was a time when one could dig a well and hit water not far below the surface. These days, the only reliable wells are the ones that adjoin large green spaces — like the maidans for example.

Other cities are not so lucky and those who live where borewells are common will tell you that the wells need to be dug deeper every year. The water they reach is also an increasingly fickle seam. The demand on the groundwater is constantly on the rise but all that paving never allows it to get recharged.

Egress of Saline Water in Coastal Areas

too much paving leads to a drop in the water table which allows egress of saltwater

Freshwater is lighter than saline water

Saltwater is denser than freshwater and forces its way inland below the latter. If the (fresh) water table drops, the boundary between them is pushed deeper inland. Salinity in the soil is not merely bad for plant life but also for construction.

Trees Find it Difficult to Survive

For plants — and especially trees — paving is doubly detrimental. Not only is there very little water in the soil to help them grow but their roots are also unable to breathe. As a result, the trees develop a weak rooting system; it is no wonder so many of them topple over during the monsoons. That many of the avenue trees in our cities are fast-growing exotics, doesn’t help very much either.

Drainage Systems are Overwhelmed

Kalyan Station under water July 2005

Kalyan Station under water
Image source: Wikipedia

When it rains in an urban area that is excessively paved, the runoff has to go somewhere! That somewhere, is the storm-water system which is frequently unable to cope. This leads to the all-too-familiar floods we see every year.

At best, flooding is an inconvenience but, as the last few years have shown us, it can also be deadly. Corrupt builders, politicians, and bureaucrats are responsible for the rampant encroachment on natural drainage channels in many of our cities. This results in the kind of devastation and loss of life we saw in Bombay (2005), and Madras (2015).

No doubt, in both cases there had been uncommonly heavy rainfall. We must remember, however, that climate change is causing an increased frequency of such extreme events, so it would be foolish to brush them aside as a freak events.

Worsening of the Urban Heat Island Effect

urban heat island

Temperatures are significantly higher in cities
Image source: Wikipedia

Paving is one of the major factors leading to the heat island effect — that phenomenon where an urban area is significantly hotter than its surroundings.

Unlike soil which cools off rapidly when the sun goes down, paving retains heat for longer and then emits it slowly through the night. One of the only ways to reduce this effect is to increase the area under plantation (including on roof terraces). However, as we have seen earlier, that is rather hard to do, when everything has been paved over. It’s a bit of a vicious cycle.

What We Need to do

Of course the very best thing to do is to avoid paving as far as possible. However, there are many situations when we really have no choice. At such times, the least we can do is to use materials and systems to mitigate the problems we cause.

Pervious Concrete Paving

permeable concrete

Permeable Concrete
Image Soure: Wikipedia

This is a type of concrete where the fine aggregate (sand) is missing so that the concrete becomes porous enough for water to percolate through. This means, of course, that it is not as solid as other concretes and cannot sustain the same heavy-duty usage. On the other hand, it is perfectly usable in areas where traffic density is low or, for example, in parking lots.

Some cities like Portland, Oregon in the USA have experimented quite extensively with permeable paving. Unfortunately, there is little sign of anything even remotely close being done here.

Perforated Paving Block or Grass Paver

grass paver blocks

Grass Pavers
Image Soure: Wikipedia

These are easily available here but not as commonly used as I wish they were. They are easy to lay and, to my eye, they make a space look much nicer than if were completely covered with a hard surface.

Permeability is excellent but, like porous concrete, it can only be used for low-traffic areas or parking lots.

Tree Guards

tree guard

Tree Guards
Image Soure: Flickr

If all else fails — and even if not, it is wise to have tree guards which allow the soil around the roots to breathe. This is something that is conspicuously lacking in our cities.Instead, we see a low brick wall made as close to the trunk as possible. Apart from being undersized and ugly, these are also tripping hazards for pedestrians.

It would be so simple, instead, to embed a cast iron tree guard that is level with the pavement. If the city authorities feel that the iron will be pilfered, they can do something similar in ferro-crete. It won’t look half as nice but at least it will be effective.

Green Roofs

green roof

Green Roof
Image Source: Wikipedia

While a green roof can’t do very much for the surface runoff and the storm-water systems, it can certainly be help reduce the urban heat island effect.

Planted roofs haven’t caught on too well here as yet. That will not change until waterproofing systems become much more reliable. People who have running battles with monsoon leakage are unlikely to tempt fate.


The situation is far from ideal but it isn’t a lost cause just yet. Given enough awareness and pressure from the general public, things can improve. Organisations like depave, for example, have done this very effectively. They have not only raised awareness in Portland but have even forced the local government to reverse past mistakes.

Maybe it’s time to start something like that in all our cities here as well.

Planting for Birds & Butterflies

Plants that you should consider

There are a number of things you can do to attract butterflies and birds to your garden. Here is a basic list that may be useful as a starting point for people living in peninsular India. Please remember that this list is neither complete nor comprehensive because habitats vary so dramatically across our country. I’ve tried as far as possible to list local species but some, like the Lantana, have naturalised in our country and have therefore found a mention.


A number of butterfly species lay their eggs on grasses – but not of the cultivated kind. Unless you have a very large plot, it is unlikely you’d want to allow these to grow. However, if the possibility exists, it is nice to let a patch of garden in a corner somewhere actually grow wild.
Bamboos are food for some butterfly species and refuge for many birds and other creatures. Keep them a little distant from your house if you’re petrified of snakes, though.

Shrubs and Creepers


Even if you live in the heart of a city like Mumbai, you will be surprised by the variety of birds you can see if there is enough greenery around. I’ve seen the beautiful Paradise Flycatcher in Breach Candy which is, barring a couple of tiny green pockets, as concrete a jungle as you can get.

Although the links above all point to wikipedia, a very good resource I have found for Indian plants is Flowers of India. The site aims at having comprehensive information about Indian flowering plants with their common names (especially in Indian languages), pictures and details of habitat and distribution.

Preventing Soil Erosion

Erosion of soil is a very real problem that can crop up when we encounter sloping land on a site. In this article, I’ll outline the measures taken on two different sites where erosion needed to be controlled. The first was done entirely via plantation and the second (where the foundation of a building had to be supported) involved terracing of the land — in conjunction with plantation of course.

Slope Stabilisation with Vetiver

In the year 2003, a client of mine wanted to buy an 11 acre plot of land along the Narmada river. It was a lovely location but the soil was very soft and powdery and the land was scarred by deep fissures where rainwater flowed down to the main river. What made it downright dangerous was that these steep gullies were collapsing at points and something needed to be done before parts of the plot got cut off and became inaccessible.

At the time, I suggested reducing the angle of the slopes and planting local reeds that grew along the riverfront to hold the soil. The first part worked but the second did not. The wild plants refused to grow where we wanted them to and something else needed to be found. That’s when she decided to try growing Chrysopogon zizanioidesVetiver (also called Khus).

What happened next was almost miraculous. The Vetiver took hold of the soil and bound it in a way that not only stopped erosion but allowed rainwater to seep into the soil instead of letting it all run off to the river. As a result, even the trees growing in the gullies got healthier and what looked like an almost barren landscape then, is now a great example of how working with mother nature is far more productive than trying to fight her. And plantation costs a fraction of what it would if we used “man-made” solutions.

What makes Vetiver different from other grasses is the fact that it’s roots do not form a horizontal mat like the others but grow downwards as far as 4m (13 feet). Another good thing is that it propagates in a way that makes it easy to control – so it doesn’t become an invasive weed.

To know more about Vetiver and how to use it for erosion control, go to the Vetiver International Network Website and download their manuals, videos and presentations.

Terracing the Land

Now, while I’ve been extolling the benefits of natural solutions, there are times when we simply have to use brick and mortar solutions when structural demands have to be met. The [RaBV] bungalow at Nasrapur was built on steeply sloping land and we not only had to prevent erosion but also make sure that the building’s foundations had rock solid support even if an earthquake struck. In such a situation, simply planting Vetiver, or any other vegetation for that matter, would never have been sufficient.

The first thing to do in the design was to follow the slope of the land as closely as possible. The main floor level was split with the living room sunk by about 0.6m (2 feet) from the rest of the house. Then, the verandah which projected by 2.4m (8 feet) beyond the house line was almost 1.8m (6 feet) above surrounding ground level so instead of filling it up, a little earth was excavated and an extra level – like a basement – was created below the verandah. Not only did this reduce loading on the peripheral foundation wall in a big way but is also served as a space for garden implements, a separate room for rainwater harvesting tanks and parking for a motorcycle.

The verandah effectively then, became the first terrace. Then, to buttress the foundation, a second terrace was created just in front of the basement. Here, we planted only shrubs and bushes – nothing with strong roots that might weaken the stone wall at some future date. Finally, we built a retaining wall to support the second terrace.

Maybe it was unnecessary to go so far but, when there is going to be no second chance to correct a mistake, you tend to err on the side of caution. Around the bungalow, on non-critical slopes, local vegetation has been allowed to grow naturally and has taken root well enough to protect against erosion.

Planting for Nature

The lives of birds and insects are so closely intertwined that you’re unlikely to have one without the other and both are extremely dependent on plants for shelter and sustenance. In nature, nothing works in isolation so, if you want to attract what are generally considered “beautiful creatures” to your garden, you have to be willing to accept the less popular ones. If you want butterflies, you will also have caterpillars and if you want birds you have to be willing to accept all manner of insects – some of which will attack your plants.

Despite that, it is extremely important to avoid chemical pesticides and fertilisers that will either kill them or drive them away. Unlike plants that are able to selectively repel certain types of creatures, man-made chemicals are less discriminating. Instead, if you want to keep the caterpillars (and other plant-eating insects) in check, make sure your garden also attracts birds. Butterflies and their caterpillars are themselves food for many birds and if the garden isn’t attractive to birds, the caterpillars will eat everything in sight. It’s just part of the balance of nature.

This page gives a list of trees and shrubs that you could plant to attract both, birds and butterflies. I have not given separate lists because the two of them pretty much sail and sink together.

Ways to Attract Butterflies

Creating a garden that consistently attracts butterflies is not all that difficult. You don’t necessarily need a lot of space – although that naturally helps – but you will need to learn a bit about these beautiful creatures before you begin. What this page will give you, is only a primer to start you off because the species of butterflies found in different parts of our country vary quite dramatically.

The first thing you need to provide if you want to attract these beautiful creatures to your garden, is a habitat they can be comfortable with. This means planting everything from dense shrubs that shelter them from predators and rain to tall trees (which some of the larger butterflies frequent in an activity known as “tree-topping”) while also leaving open space for them to bask close to the ground. Being cold-blooded insects, they need to warm their wings in the sun before they can take flight in the morning.

The second thing you need to do is bribe them outright! Many (though by no means all) adult butterflies feed on the nectar of flowers. In doing so, they act as couriers for the pollen grains that stick to their bodies, thereby helping in pollination making it a symbiotic relationship. By and large, butterflies prefer to visit multiple small florets as opposed to single large flowers so you might want to look for plants that have these characteristics. It is helpful to have a variety of plants so that their different flowering seasons ensure availability of nectar through the year.

The third important thing that most people don’t realise is that it is not enough to merely attract the adults; if you want their continued presence, you must provide for their young as well. Caterpillars (and here’s something you might not know) are very specific about the plant they feed on. Caterpillars of any given butterfly species will only feed on a single plant species or sometimes a bunch of related plant species. For instance, many of the smaller lycanid caterpillars will only feed on grasses while, say, a tiger butterfly will hunt for a certain milkweed (Calotropis) on which to lay her eggs – and a Red Pierrot caterpillar will restrict itself to the fleshy leaf of Bryophyllum. Put the red pierrot caterpillar on a tree full of juicy green leaves and it will simply die of starvation.

One more thing that is easily provided and will attract a lot of male butterflies during the dry months is a patch of damp earth. Males flock to such patches for “mud-puddling” wherein they get salts and other nutrients from the soil which they need to be considered eligible by the females. And if you really start getting addicted to butterflies, you can also bait some species with rotten and fermenting fruit; the little alcoholics will simply love you!

How to Attract Birds

Like butterflies, birds also require a variety of plant types to make them visit your garden. Some birds like thrushes and babblers prefer to forage in the shade, Sunbirds go to nectar-rich flowers while parakeets and Barbets want to get at fruits and seeds that are usually found in the larger trees like the fig. One therefore needs to plant a tiered garden with patches of sunlight on the one hand and dense shade on the other. Also, birds usually prefer local vegetation so keep that in mind when you do your plantation.

Install a bird-bath. It’s not very difficult to make and as long as you don’t have cats as pets (or neighbours), the birds will give you hours of enjoyment. There are numerous pages on the internet that explain how to make a birdbath. Just one thing to remember is that if you leave the water stagnant, you will be breeding mosquitoes – not a pleasant thing.

The trees you plant should be dense and shade-giving. These will give great shelter for roosting or even nesting. And if they happen to be fruit-bearing, that is even better. Bushes, especially flowering ones, should be planted around the trees in clusters instead of scattered all over the place.

As with any nature-friendly place, you should avoid (or at least minimise) the use of chemical fertilisers and pesticides. Pesticides will eliminate a broad range of insects and spiders some of which you may not be very keen on but which are extremely attractive to our feathered friends. A garden devoid of insects will get very few birds visiting especially during the nesting season when they’re foraging for their young. Nothing exists in isolation in nature and if you want to look at pretty creatures, you’ll have to learn to look at and enjoy the ones that aren’t as popular.

Site Ecology & Building Footprint

Tread Lightly on the Land

In my experience developers, who are trying to sell multiple plots of land, often spend huge amounts of money completely flattening everything in sight. We are then left with a veritable desert because he has also chopped ever tree, ripped out every bush and completely eliminated the ground cover – not to mention mixed the fertile topsoil with the useless layer underneath. Worst of all, he has managed to completely destroy the natural drainage patterns of the entire development and many others downstream as well.

It is not correct to blame the developer alone for such a situation. He is doing this because he believes that unless he provides a completely level a plot, it will never sell. The demand for levelled land often comes from the clients and, in some cases, their architects. So unless the promoter of the project is already enlightened on the environmental fallout of such indiscriminate levelling (or if he is somehow made aware before the bulldozers move in) this is a very common scenario.

It doesn’t have to be this way and there are a number of things we can do to preserve the ecology of a given site.

Preserve Topsoil

Topsoil is the uppermost layer of the earth – just a few fragile inches of organically rich soil that allows the growth of plants. On average, it is said that a single inch of topsoil takes a century to be created. This, then, makes it imperative that we do all we can to preserve and protect it. Almost always, during construction activity it is lost and, once the building is built, new topsoil has to be imported from somewhere else thereby making some other land infertile.

Pretty senseless, isn’t it?

Now it is a labour-intensive process to take off a layer of topsoil and store it for the duration of construction but it is by no means difficult. All it needs is for the clients to be willing to pay a tiny fraction extra of the total project cost even if the average contractor thinks they’re loony.

The topsoil can be piled in a corner of the site (or stored in bags) where is doesn’t come in anyone’s way and then spread out where required when the landscaping is to be done.

Keep the Existing Vegetation

Every piece of land has a certain character that makes it what it is. Unless you’re buying a plot in a development where everything has already been killed, this character are probably what attracted you to that particular piece of land in the first place. So then why do we not preserve the vegetation as much as possible. Sure, we’re sometimes faced with impossible situations and have to cut a tree or some bushes. In such cases, we should replant at least three times the number to compensate.

More often than not, we can save trees that are “in the way” and actually make them an important part of the design. This needs for the architect to be creative and, equally importantly, for the contractor and his team to be sensitised to such a requirement. From experience I have found that a contractor, labourer or even a truck driver delivering material to the site considers them to be obstacles that must be gotten rid of because they hinder the free flow of materials and labour. Contractors must therefore be made aware before the work starts that you are very keen on protecting such vegetation. If you think you can safely tell them at some “appropriate time”, it will probably be too late.

Maintain Drainage Patterns

A plot of land doesn’t exist in isolation. It is merely a small part of a large jigsaw puzzle that covers the entire earth. In non-urban settings, especially in areas of high rainfall, any water that passes through your land eventually goes to someone else’s. If we change that and either block the water’s entry into the site (or exit from it) we are interfering with the overall system.

While it is true that even natural drainage patterns often change on their own, they do so only when there is an alternative. Suddenly blocking the natural flow of water is either foolhardy (if you’re trying to keep every drop out) or selfish (if you’re trying to keep every drop to yourself).

Again, sometimes we have to modify a watercourse but it should be done in such a way as to not affect the people who live downstream. For example, there was a site in Zirad, Alibaug, where the entire plot, especially the part where the house was to be built, would be flooded during most of the monsoon making it potentially impossible for the clients to enter or leave the house during those months. Their early attempts to make a straight stone dam at the point where it entered the site came a cropper when the first rains washed it away. Surprisingly, this dam had been suggested by the local villagers – which leads me to believe that they’ve been living off the sale of land (instead of what they produced from it) for far too long.

While there is no static rule for dealing with storm drainage the attempt should be two-fold:

  1. Try and preserve the entry and exit points for water to and from your site
  2. Allow the water to flood gracefully. Trying to restrict it too much will invite trouble at some stage. The massive flooding in Bombay (Mumbai) in July 2005 was a result of the Mithi river being constricted to such an extent that, by the time it broke its embankments, it had swollen to unnatural levels.