29 Feb 2012

Too Much Water

Posted by bcsands

‘Too much water’ isn’t a phrase that we hear very much in Australia – usually it’s the opposite. But after years of drought, heavy rainfall in New South Wales, and other areas has caused some unexpected problems.


Unusual weather such as drought conditions or heavy rainfall can cause ground movement and subsidence under your home. The ideal condition for stable foundations is for moisture levels to be consistent over time – but the Australian weather conditions often fail to cooperate. Houses built on clay can be particularly vulnerable, as a clay soil will shrink in dry conditions and expand when it is moist.  In the case of a drought, another problem can be tree roots, which can undermine foundations as they search for water under your property.

The most obvious warning signs of subsidence are diagonal cracks that suddenly appear on brickwork and also on the plaster inside. Small cracks in walls are normal, but subsidence cracks are larger and usually wider at the top. Doors and windows sticking, cornicing pulling away from the ceiling and flooring forming ridges or bubbles may also point to a subsidence issue.

Most homes are flexible enough to handle some amount of subsidence without sustaining serious damage. Some cracks may open and close, depending on the level of moisture in the soil, without being any great cause for concern. However, if a crack is growing consistently, or dramatically, it might be time to consult a structural engineer.

Site run off

Local councils have stringent rules on site run off – and heavy fines, sometimes of thousands of dollars, for guilty parties. During heavy rain, a builder must ensure that site debris, building supplies and mud are not washed off site and onto surrounding roads and properties. Perimeter and drain protection, stockpile containment and stormwater management are achieved by using products such as silt fence, straw bales, sand bags, filter socks and/or Bio Sock.

Garden erosion

Plants need water – but not too much! A deluge can erode your garden beds, washing away your most fertile top soil, taking seeds and seedlings along with it.

Constant rain can also lead to waterlogged soil, which is as bad for your plants as dry soil. Clay-based soils are particularly prone to this. Too much water in your soil reduces the oxygen and other nutrients available to your plants, resulting in rotting roots and plants that develop fungal and other diseases. Seeds are even more vulnerable – they need a good balance of moisture and heat to germinate, and too much water will kill them.

Some of our most iconic Australian plants require very little water to achieve their most impressive growth. For example, Frangipanis may drop leaves and are reluctant to flower when overwatered.

We can’t do much to stop the rain, but make sure that rainfall is running off your garden beds, not pooling around your plants. Watch how heavy rainfall is distributed around your garden – avoid planting in areas where water flows, or divert the water to another area using barriers. Consider drainage for any areas that seem to be permanently damp. Help your plants to compensate for lost nutrients with fertilisers and compost – and avoid planting when heavy rain is due.

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