Lewis Road has been identified as having significant roadside vegetation and is lined with remnant Yellow Box, Grey Box and River Red Gum. The recent flood events have seen a significant number of very large trees falling and in many instances taking with them large branches of adjacent trees.
Trees have been failing in the lower lying areas near Chinaman Creek where we find most of the Yellow Box and Red Gums. This phenomenon is rarely seen out in the open paddocks. Why is this so?
As we know the rainfall has been extraordinarily high in the past 6 months and soils have reached saturation point. Wet soils have a lowered shear strength (holding ability). Considerable loads are applied onto the tree root system from the mass of the tree coupled with the additional weight of water in the canopy. Add some wind gusts and the tree’s stability can be compromised.
Roadside trees have usually developed in groups where adjacent trees buffer wind forces. The tree roots do not need to develop as broadly as trees growing in the open where they are more exposed to constant environmental impacts. Healthy trees are marvellous biomechanical structures that can self-optimise when injured or stressed.
We humans have our inputs too. Roadside vegetation is subject to repeated patterns of disturbance from activities such as road grading and drainage works. As trees age they are less able to tolerate change in their environment and have reduced energy reserves available for adaptive growth.
We also have some fallen giants that are now sending up shoots from their horizontal trunks – even they they seem to be almost wholly uprooted.