The Lourens river takes most of the water out but the railway line, roads, N2 freeway, and not even mentioning the many buildings, interfere with the natural draining of the area and accumulates the water in the cache area. One of the main roads from Somerset West goes underneath the railway bridge, so does the water.
The dunes by the sea are higher than the inland area and are built upon with high residential and holiday flats. These have deep foundations that will slow down any seepage through to the sea. Hence the damming effect. This causes a flooding problem for residents living in the “dam” area. In winter, when it rains the most, flooding can occur quite easily and to prevent this disaster, manmade flood plains were created to collect the water, direct it to a single entrance to a pipeline that will guide the floodwaters safely to the sea.
At the cache area, one can easily observe the entrance of the pipeline. Look around and realise that none of the houses in the area would have survived a single winter without this manmade drainage system.
The system is divided by dirt walls that were thought to be a good idea to be planted by trees so the roots could strengthen the walls and also for the trees to use the water. It is just a pity that they did not use indigenous trees. Use your aerial view again to see the arrow shape of the trees. (Also the arrow indicates the GZ used in the hint)
Well, I thought it a good place to leave a cache. It is at least one other good use for an Australian tree. (Eucalyptus globulus)
My father’s house is very close to this system and I used to take a lot of walks in this area. It is a nice quiet “park” if you like, where one can take a dog for a walk or just stroll and enjoy the peaceful environment. You will always find some water birds and guinea fowl. In summer time, it dries up completely and I have noticed 4x4 enthusiasts testing their vehicles by driving in and out the “dam”. I doubt if that is legal so I do not suggest anything of the kind unless you want to get a stiff fine.
The cache is a pet ID nano and hidden in the closest object seen in the picture of GZ.