Morocco swapped scorching black asphalt for porous “sponge” pavement; the experimental surface ran up to 16°F cooler, offering cities a surprising new way to beat urban heat

On a scorching summer day, a city street can become more than just a route for traffic. Dark asphalt absorbs the sun’s energy, stores heat and releases it back into the surrounding environment, adding to the discomfort of already hot neighborhoods. At the same time, when heavy rain arrives, the same sealed surfaces can send large volumes of water rushing toward drains and sewers.

Now, limited experiments reported in parts of Marrakech and Agadir are exploring whether pavement can work differently. Instead of relying entirely on conventional bitumen, selected urban surfaces are being tested with permeable pavement that enables water to move below the surface. The approach, sometimes termed as “sponge” pavement, could offer two potential advantages at once: better management of rainfall and lower pavement temperatures when moisture is available.

The idea is attracting attention because some cool-pavement experiments elsewhere have produced temperature differences of up to 16°F. However, that figure comes from an Arizona pilot cited by the U.S. Environmental Protection Agency, not from the Moroccan trials. Morocco's experiments remain limited, and the available reports do not suggest that the country is replacing black asphalt nationwide.

How Morocco's “sponge” pavement works

Moroccan media report that selected regions in Marrakech and Agadir are being used to test permeable pavement.

Unlike conventional asphalt, which creates a largely sealed surface, permeable pavement contains interconnected spaces that allow rainwater to pass through. Water can enter a stone layer beneath the pavement and, where soil conditions permit, continue into the ground.

This changes the way rainfall behaves after it reaches the street. Instead of immediately flowing across the surface toward a drain, some water can be temporarily held beneath the pavement.

That stored moisture can also contribute to cooling. As water evaporates, it takes heat from the surrounding material. The principle is similar to how evaporation of sweat helps cool the human body. When enough moisture is available, this process can lower pavement temperatures while also slowing the rapid movement of stormwater.

The approach is associated to the wider “sponge” city concept, which uses urban infrastructure to absorb, store and manage rainfall rather than treating every drop as runoff.

Why conventional asphalt contributes to urban heat

Dark pavement absorbs solar energy throughout the day. Some of that energy is released later as heat, contributing to higher temperatures around roads, parking areas and other paved spaces.

This is one factor behind the “urban heat island” effect, where built-up areas can remain warmer than surrounding less-developed locations.

The problem can extend beyond the hottest part of the afternoon. Roads and other hard surfaces can continue releasing stored heat after sunset, making it harder for urban places to cool down during hot weather.

Where the 16°F figure comes from

The potential temperature reduction connected with alternative pavement designs can be significant, but the 16°F figure requires context.

During an Arizona pilot cited by the U.S. Environmental Protection Agency, conventional pavement reached about 152°F around midday. Specially designed cool surfaces were approximately 10°F to 16°F cooler.

That result features what some pavement technologies can achieve under particular conditions. It does not mean the Moroccan permeable pavement has been measured at 16°F cooler than conventional asphalt.

The EPA's research emphasizes that pavement characteristics and local conditions influence how effectively a surface can reduce heat.

Moisture is critical to the cooling effect

Permeable pavement does not remain cooler under every weather condition.

After rainfall, water can remain within the pavement system or its underlying stone layer. As this moisture evaporates, heat is removed from the surrounding surface.

Research summarized by Rutgers University discovered that permeable concrete released around 25% to 30% less heat than conventional concrete on days after rainfall. However, on dry, sunny days, the permeable concrete could release slightly more heat.

The finding illustrates a central limitation of evaporative cooling: it relies on moisture. Once the stored water has disappeared, the cooling effect becomes weaker.

That makes local climate, pavement design and rainfall patterns significant factors in determining whether the technology will offer a meaningful temperature benefit.

Marrakech's wider sustainability program

The pavement experiments fit into a larger climate-resilience attempt in Marrakech.

The “Marrakech Sustainable City” program was launched in 2023 and brings together Morocco’s Ministry of Energy Transition and Sustainable Development, local authorities, the United Nations Development Programme and the Global Environment Facility.

The program addresses climate resilience alongside mobility, waste management, biodiversity and energy efficiency.

It has $9.5 million in Global Environment Facility funding and is expected to directly benefit more than 1 million people.

The pavement experiments are one potential tool within that wider agenda, illustrating how ordinary infrastructure could become part of climate adaptation. The information of Marrakech's broader climate-resilience program was published on Marrakech Durable.

A possible benefit for pedestrians and neighborhoods

The wider impact could be felt at street level.

Roads and parking regions can radiate considerable heat into nearby spaces. Minimizing the amount of heat stored by these surfaces could make walking routes, bus stops and outdoor public places more comfortable during hot periods.

A single section of cooler pavement would not transform a complete neighborhood. But if pavement changes are combined with shade trees, reflective surfaces and other heat-reduction measures, their collective effect could become more noticeable.

Why permeable pavement has limitations

Permeable pavement cannot simply substitute conventional asphalt on every road.

Its open spaces can become blocked by fine dirt, tire debris and sediment. If that happens, the surface can gradually lose its ability to absorb water. Periodic cleaning and needed stormwater design are therefore required.

Heavy traffic and extreme vehicle loads can also limit where specific permeable systems can be used. Polluted runoff presents another consideration because planners must find how contaminants are handled before water enters the ground.

For these reasons, permeable pavement is often more suitable for sidewalks, plazas, parking areas, rest areas and lightly traveled streets than for each major highway or heavily trafficked avenue.

Source: ECONEWS

FAQs:

Q1. What is permeable pavement?

Permeable pavement is designed with connected spaces that allow rainwater to pass through the surface. The water can then move into underlying layers and, where conditions allow, into the ground.

Q2. Why is Morocco testing this type of pavement?

The approach could help cities manage both urban heat and stormwater. It is being explored as one possible tool for climate adaptation.