Our Need and Obligation to Reduce Impervious Cover [ John Cornacchia ]

John Cornacchia at Globacorp Developments International writes:

Impervious coverAquifer Diagram

Impervious cover, also known as impervious surface, refers to any surface that water cannot easily penetrate. Ranging from roads, parking lots, driveways, patios, walkways, curbing, building rooftops, public buildings, and commercial structures, impervious cover prevents moisture, rain, and snow from soaking into the earth’s surface, thereby generating harmful stormwater runoff. Stormwater runoff carries organic matter, fertilizers, pesticides, grease, oil, and other contaminants into our ponds and streams, and more importantly, our precious aquifers.

In addition to changing the quality of the water running into our water bodies, impervious cover changes the quantity of runoff, essentially eroding and changing the physical structure of existing streams. Since water runs more rapidly off of an impervious area, flooding becomes both more common and more intense downstream. Meanwhile, because less water is soaking into the ground, water tables can drop and eventually streams and wells fed by groundwater begin to dry up.

All of these effects can be observed in developing areas of the world, even if there is enough open land remaining to absorb the extra runoff and dilute the pollutant load so that impacts are minimized. However at some point, the balance is tipped and permanent damage to water quality and habitat can occur. The direct cause of the damage depends on the nature of the runoff and the particular topography, soils and vegetation on a site. For example, when the native trout vanish from a stream, it is often very difficult to determine the exact cause. Is fertilizer in the runoff creating algal blooms that deplete the oxygen in the water? Are flash floods spoiling spawning gravel beds? Are water temperatures rising? Or is it some combination of factors? As scientists worked to understand these processes, it became clear that in most cases there is a direct correlation between the degree of water impairment and the overall amount of impervious cover in the watershed. While it is difficult to predict which factor will impact any particular situation, certainly as impervious cover rises above 10% there is almost always a measurable loss in water quality. Impervious cover between 10% and 25% dramatically increases these impacts, and both pollution and flooding are visibly evident. Above 25% impervious cover, water quality impacts can be so severe that it may not be possible to restore water quality to pre-existing conditions.

To learn about impervious cover and sustainable development, John Cornacchia invites you to visit Globacorp Developments International at www.globacorp.com.

For communities interested in protecting water quality, natural ecosystems, and the prevention of flooding, it is very difficult to measure, let alone manage, the multitude of separate factors that can potentially impact various watersheds. However, because of the well-documented correlation between impervious cover and stream health, there is an opportunity to use impervious cover as a surrogate for both measuring and managing water quality and watershed health. By maintaining overall impervious cover to below 10%, communities can ensure that the land will be capable of absorbing and filtering runoff from developed areas and preventing excessive flooding, ecosystem impairment and contamination of water supplies.

It is important to understand that approximately 75% of the streams that feed our water bodies with clean water are small headwater streams that are often small enough to be straddled by a child. These streams are extremely sensitive to land use changes and are therefore very susceptible to contamination. If the level of impervious cover rises excessively in these areas, irreversible damage can occur to drinking water quality, to groundwater supplying private wells, our precious aquifers, and to aquatic wildlife habitat. As communities continue to develop, there will be increasing pressure to replace natural areas with additional impervious cover. Even when best management practices are widely used when attempting to mitigate the impacts of impervious cover, a threshold of impervious cover is eventually crossed, beyond which predevelopment water quality cannot be maintained.

Now more than ever is the critical time for all developers to evaluate the potential impacts of future development and associated impervious cover on the health of the world’s water bodies. It is important to note that it is not growth itself that is the problem, more it is the way that communities require growth to occur that is the issue. By continuing to adopt more innovative land use techniques and development standards, developers can guide growth away from sensitive areas to those sites that can better accommodate it. Furthermore, by reducing impervious cover utilizing improved site design and a range of sustainable construction practices, the health of the watershed can be protected and flooding minimized even as growth continues.

To learn about impervious cover and sustainable development, John Cornacchia invites you to visit Globacorp Developments International at www.globacorp.com.

We at Globacorp belief that our water bodies are critical to the survival of the planet and are genuinely doing our part to reduce the impact our communities and operations have on the environment. We are strategically planning and engineering our community developments to reduce the amount of impervious cover, thereby continually improving the quality of life for everyone, now and for generations to follow.

Our latest efforts, Paraiso Del Rio Grande Resort Community, with an impervious cover under 10%, will certainly be one of the most sustainable and green residential developments in the Americas, revitalising over 100 Hectares of previously slash-and-burn land located in Coclé, a central province of The Republic of Panama.


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