I’ve always been a bit of a weather buff so the recent rainfall we’ve experienced in south-western Victoria has been interesting to say the least. In the middle of June we constructed a sandbag weir at Cashmore, just to the west of Portland. After a fairly wet start to July we revisited the site and, after consultation with the landholder, dropped the weir by about 200 mm, or a row of sandbags. The rainfall chart below shows how much rain fell in the weeks following construction.
The weir was designed to withstand overtopping but what we didn’t expect was an event of the magnitude which occurred on 14th August, with 61 mm falling within a 24 hour period. This was a daily record for August and came on the back of the wettest July since records began in 1982.
I dropped in to check on the weir the day after the big event fearing that the structure may have been compromised, but to my relief, I found that it was holding up and still allowing flow within the confines of the drain. There was water everywhere this day with localised flooding, road closures and even severe damage to the Bridgewater Rd. You can view a short video which illustrates how the wetland and flow rates have changed over this period.
The whole event proved that, through good design consideration and drawing on local experience, even temporary low-cost trial structures can be managed for optimal water retention.