Necessity of Permeable Pavements in Nepal

If you are 25 years old like me, and have been a resident in Kathmandu for a very long time, you may remember, Kathmandu was full of agricultural land and houses were scarce. There were fewer roads and less concrete. Due to haphazard urbanization, now in this modern day, we see more concrete and less agricultural land and no open space. Houses are rampant and everything in between is covered by roads and footpaths. This has not only seriously affected the ergonomics of the city, but the environmental effects are equally greater.

Urbanization has severely affected the city landscapes of Nepal. By replacing natural land covers (like grasslands and forests) with impermeable surfaces (like parking lots and streets), we lose the water retaining role of the soil and vegetation. Increased runoff from impervious surfaces has caused dangerous floods in the Terai cities, and even some areas in our capital such as Balkhu, Kuleshwar, Balaju,etc.Diminished recharge of groundwater has dried out almost all of the wells of our capital. Not only these same impervious surfaces reduce the natural absorbing capacity of our planet, but can also transport the many pollutants deposited in urban areas, such as sediment, bacteria, pesticides, and chloride into the local waters.

The people in Kathmandu usually depend on the ground water for fulfilling their daily water needs. But irregular monsoons due to climate change have caused the underground water level to diminish. In addition to that, with the onset of the dry season , people in Kathmandu valley face shortage of drinking water with more than 50% depending on underground water. Similarly due to haphazard urbanization, there is no space for water to get soaked in the ground. However the demand for underground water has risen with no water able to go inside the ground to compensate equally for the used water. 

The stated problems are the effects of inadequate ground water table recharging. So, what is ground water table recharging? It is a process of water seeping through the soil and filling in the empty spaces and cracks below the ground. The infiltrated water passes through the unsaturated region of groundwater and joins the water table. It is based upon soil type, land use, land cover, geomorphology, geophysical and climate (viz. rainfall, temperature, humidity etc.) characteristics of a region. Recharging of groundwater takes place by the rainwater and water present in the water source like rivers and ponds. 

The problem of diminishing underground water can be solved by different direct and indirect methods of groundwater recharge technology. Two of them are using recharge trenches and permeable pavements which facilitate the percolation of water through the soil at shallower depths. These technologies can reduce the wastage of water and enhance groundwater availability for uses in different sectors like irrigation, domestic and industrial uses.

Efforts to reduce the impacts of urban runoff have already started in the developed countries, and some residential areas of Nepal, but it is also necessary to incorporate them in the public areas such as driveways, bikeways and sidewalks. We already know the tremendous benefits of permeable pavements and therefore incorporating them only means better for the urban environment.

What is Permeable Pavement?

Permeable pavements consist of specially designed pavers, stones,concrete or bricks that allow water to soak into the ground below. They are made of either a porous material that enables stormwater to infiltrate it or nonporous blocks spaced so that water can flow between the gaps.In addition to reducing surface runoff, permeable paving systems can trap suspended solids, thereby filtering pollutants from stormwater. This eco-friendly pavement is commonly used in patios, parking lots, sidewalks and driveways, and is suitable for light traffic, cold or hot dry climates,and shallow slopes. 

What is a grass paver?

One such permeable pavement is a grass paver which is Eco-Friendly with a high degree of water charge(permeability). It allows lush green landscaping by allowing good growth of green grass around it.

Benefits of Grass pavers

Some advantages of laying down grass pavers include:

1. Ground Water Recharging: Impervious concrete pavement constructed in an urban area,recharges water directly into the subsurface and conserves it, while tackling the growing problem of ground water level declination.
2. Reducing Heat Island: Permeable pavements enable greater retention of water in the urban landscape, which are at greater risk for high temperatures due to the heat island effect. Similar to green roofs, they keep the water within the local micro-ecosystem, which in turn keeps temperatures cooler when compared to a non-permeable paving system.
3. Managing surface runoff: Large volumes of urban runoff causes serious erosion and siltation in surface water bodies. Permeable paving surfaces have been demonstrated as effective in managing runoff from paved surfaces, and therefore can reduce downstream flooding and combat erosion.The goal is to control stormwater at the source.
4. Appropriate for Colder Climates: Snow and ice will take longer to accumulate and will melt more quickly on permeable pavers due to tempered airflow in the base drainage layer of the paver system. This keeps the surface temperature of permeable pavers warmer and proves to be a safe surface for driving and walking.

Preventive Maintenance

It is important to remove debris from the pavers by sweeping regularly.The pores should be clear of fine aggregates so as to not hinder the system’s ability to infiltrate stormwater. The patio or driveway should be observed during the rain to make sure water is flowing through the joints between the pavers. Clogging can be reduced by limiting areas of loose soil near pavers. Pressure wash should be avoided to push the debris farther beneath them. Grass pavers require supplemental watering in the first year to establish the vegetation, otherwise they may need to be re-seeded. During the winter and dry seasons, grass applications might go dormant.

ASIAN GRASS PAVER : Grass Paving Stone

The Asian Grass Paver is a type of permeable pavement available in Nepal. Not only does it avoid the muddy messes from grassy lawns, but also functions as a stormwater infiltration basin. It is the next level up in landscape design, with its grassy green good looks, whether for parking spaces, terraces or walkways. Despite the many advantages, it is cost-effective as well. It also reduces the probability of accidents due to it’s high skid resistance. Cured in a heat and humidity controlled curing chamber, the installation process is less time consuming as well.

Specifications

A grass paver creates a visually appealing parking area or driveway that blends in with the surrounding lawn and other natural features, while providing a strong surface that protects the underlying grass. The use of grass pavers not only allows lush green grasses to flourish but also creates a micro-ecosystem around it. However the most desirable effect of grass paver is its ability to let water seep into the ground for ground water recharging while providing the advantages of concrete paving.

Asian Concreto also provides different types of concrete paving blocks and concrete paving tiles which help in refining the urban spaces of Nepal to make them disabled friendly.