Mary-Anne Twyman | Stabilising slopes and environmentally sound development

One of the many reasons that Jamaica is a beautiful country is because of its varied topography. The forests, however, that hold the soil on the slopes of our ‘land of wood and water’ are being depleted at an alarming rate. This results in extensive soil erosion, which in turn disrupts our lives with landslides and pollution of our water ways leading to the loss of one of our most valuable resources, SOIL.

Many of these landslides are the result of disturbances of the natural landscape through the clearing of land for agriculture, construction of roads, dwellings and large expanses of impermeable surfaces causing vast increases in surface storm water run-off. Apart from expensive ways of reducing these issues, such as building retaining walls and solid barriers, there are also many environmentally sound bio-engineering methods, that should be considered to control erosion. Soil bio-engineering is the use of living plant materials to erect structures that perform an engineering function like slope stability and erosion control.

EROSION CONTROL

For centuries, living plants and wood was the main method used to stabilise slopes. Today, some of these old techniques have been modified and re-applied. Original methods used, like grass seeding or the planting of fast-growing softwoods, have developed into new planting methods that are well-researched and used extensively overseas, but here in Jamaica they are more often than not Overlooked.

One possible reason could be, because they are not instant like erecting a wall, but require fore-thought and need to be included in a project from the outset. These installations also require an initial maintenance period, so the plants can become established. Maintenance unfortunately is something that we, in Jamaica, tend not to be very consistent about doing; however, after this initial maintenance period, the plants should be able to survive without much further assistance.

These methods of erosion protection are much less expensive and could easily be established by locals in hillside communities.

METHODS THAT STABILISE SLOPES

Plant species and methods that can be used for the stabilisation of slopes in Jamaica range from dry seeding, hydroseeding or direct sprigging with fast- growing rugged grasses, such as ‘khus khus’ grass, to the use of certain shrubs and trees, which are soft woods. These particular softwoods often have the ability to produce roots, when a mere branch alone is buried in the ground and watered, such as ‘Quick Stick’ ( sliricidia sepium), known locally as ‘living fence post’, or ‘Red Birch’ ( bursera simaruba) and there are many other suitable species.

There are many different planting methods that can be used depending on the steepness of the slope. As to which of the methods would be suitable; this must be assessed on a project-to -project basis by a professional familiar with the local conditions, current bio-engineering methods and most importantly, an extensive knowledge of local plants and their individual requirements and properties. During the planning process, it is also very useful to ask for information from locals, who having had first-hand experience of floods in their area. They can contribute valuable insight as to what takes place during a storm, and which route the flood water takes.

CONCRETE AND UNSUSTAINABLE DEVELOPMENT

Today, Jamaica seems to be in love with concrete; however, with a little fore thought it could often be replaced by much more environmentally friendly sustainable methods of erosion protection.

Developers in their desire to maximise their investment and site cut vertically into unstable slopes. After this, they are forced, at considerable cost, to build giant-retaining structures to secure the land from breaking away.

Rendered impassable

Unfortunately, in recent days, this has become all too apparent as seen on Tavistock Terrace, off Jack’s Hill Road, St Andrew, which is now rendered impassable as the road has collapsed due to an ill-thought-out development in unstable ground. The planning authorities repeatedly allow such development, when they should have been more vigorous in outlining the permitted parameters of the site and thereby be better able to influence a more-sustainable and less-environmentally-damaging development.

Our government seems to give lip service to slogans, like ‘ sustainable development’, ‘urban forestry’, ‘disasters preparedness’, et cetera, while readily permitting the concreting over of the landscape with often a total disregard of our needs, our infrastructure, our disaster preparedness and our environment.

Regarding our disaster preparedness, it seems that nobody is addressing the multitude of developments being built on totally unsuitable lands. Perhaps the terrible earthquake that has just demolished many towns in Turkey and Syria causing enormous loss of life, might shake up our planning authorities and hopefully cause them to reflect on what they are allowing to take place in some of our most vulnerable areas!

Under the guise of progress, developments are allowed, that should never be permitted and only serve to make as much profit as possible at any cost to the environment. Every developer is ultimately concerned about his own individual development; however, the government and its planning agencies are required to be responsible for the bigger picture and how our environment should be shaped for future generations.

They are supposed to use planning regulations and the foresight of our experienced and qualified planners, geologists, engineers, landscape architects and architects, et cetera. to help guide their decisions. If our politicians do not seek and follow the professional advice available to them, but continue to have a short-sighted attitude, and are more concerned about the next election, then we will certainly see many more environmental disasters due to inappropriate planning and execution of works.

This is unsustainable and we deserve better!

Mary-Anne Twyman is a landscape architect. Send feedback to columns@gleanerjm.com