How to Stop your House Flooding – A Case Study

This summer has seen an immense amount of rain falling along the coast of Eastern Australia. Flooding many houses and businesses affecting thousands of people and causing billions of dollars of damage. The impacts will be felt for a long time. We are now seeing more frequent and severe storms, flooding, and fire. With this in mind, we wanted to take a look at a case study this week about how flooding can affect properties and once it does the ways in which we can ensure future risks are minimised.  

There are two main types of flooding riverine flooding and flash flooding (otherwise known as overland flow flooding). Bureau of Meteorology has a great explanation of the two and the causes. Our case study focuses on flash flooding. Flash flooding is often more severe in urban areas where there are large areas of hard surfaces and water cannot enter the ground or be absorbed by vegetation.

This blog investigates what occurred to one of our clients who live in the southeastern suburbs of Brisbane.

Property Location

Our client’s property is in the middle of a typical suburb. There are no creeks or rivers around. It sits at a midway point on the hillside and is surrounded by houses. At the end of February was severely hit by flash flooding covering the entire internal floor in 200mm of water. As you can understand the devastation of this occurring to their home was severe.

How we Became Involved

After this event, we were called to come out and have a look at the drainage and garden to see if we could help work out how to prevent further water from entering the property. While there we took notice of some key factors that combined caused the flooding event.

• Slope and Landform – The client’s property was downhill from four houses and two roads. All these properties sloped towards our client’s garden.
• Drainage – They had a large stormwater pit adjoining their property and a stormwater drain that runs the full length of one side.
• Soil Erosion – Erosion had occurred from previous rainfall on neighbouring properties.  This was directing more water under fences towards our client’s property. Whereas previously it would have normally spread out over a wider area and although some would disperse into our clients garden it would also go to other surrounding properties.
• Fencing – One of the major causes was a fence on a property that doesn’t border our client’s. They had built a pool fence that was acting as a funnel for water coming downhill, pushing it towards our client’s property through our client’s neighbour rather than the stormwater drain which adjoined theirs.

What Did We Do?

1. In the property that installed the pool fence, several things were done. A trench was dug along the fence to direct water into the large stormwater pit rather than neighbouring properties. The pool fence was changed to a permeable fence line to allow water to flow downhill on its normal path into the stormwater.
2. In our client’s neighbours garden, the erosion was remediated.
3. In our client’s garden, additional drainage pits were installed and plumbed into the stormwater system. Vegetation and blockages were cleared from all drains. They had previously had carports and a shed with downpipes that had outlets onto turf and garden beds. There were all plumbed into the stormwater system.

What Lessons can we Take from This?

• The key to work out where the water may be coming from and note it might not be your direct neighbours.
• If water is coming from your neighbour’s property, talk to them about it first with ways you resolve the issue together. If they are unwilling to talk to you about it your local council may be able to help.
• Contact your local council if the water is coming from the road or adjoining council land.
• Unclog drains where possible, or get a professional to help.
• You or your neighbour may need more drainage in your garden.

Don’t Forget the Legals

Be aware of your legal responsibility when it comes to overland flow. You are legally required to accept overland flow onto your property. It is your responsibility not to alter your property to push more water directly into neighbouring properties. There are ways to deal with water flow so it doesn’t go places it shouldn’t.

If you would like to talk to us more about water and drainage issues on your property, contact us and we are happy to come and help.