Investigation of First Creek & Assessment of riparian zone

 

Observations of the First Creek

The First Creek itself looks quite healthy. The water is clear and flows quite quickly due to the slope of the river. Ducks can easily swim against the current of the creek. Even if leaves are dropped into the water, it will most likely be swept away instantly.

Areas of erosion including cut banks are located mostly on the outer side of bends. The inner side usually has deposition and point bars. Areas of erosion are located close to areas of deposition. The First Creek has many bends and most of those bends have areas of erosion and deposition.

First Creek only flows after precipitation occurs close to the Mount Lofty Ranges. It is ephemeral. Water levels are therefore normally very low. Low water levels result in more riffles. The water will also flow more quickly. Flowing water rarely gets dirty.

There is quite a bit of rubbish presumably blown from Marryatville High School that gets caught on rocks. These pieces of rubbish are mainly composed of plastic. The school car park is only 10 metres (at the most) from the creek. The runoff travels on the surface of the car park and into rainwater drains. The car park bitumen affects the water quality of the creek. Nitrates from fertiliser, phosphates from detergents and oil from cars are all factors that contribute to the pollution of the creek. The excess nutrients increase the scale of algae blooms. The oil and other particles enter the creek via runoff. These are not easily seen by human eyes. Oil can be toxic to aquatic life and plants. Australia should change policies to make sure that out dated old cars are not used on Australian roads. The exhaust fumes are absolutely disgusting. There are virtually no old cars in Japan. This is due to rules that are in place to keep people buying new cars after several years. The Japanese government supports the car manufacturing industry. Salt leached from the soil surrounding the creek affects the salinity of the water.

During my investigation, I only found two pools that seemed to be pools but flowed a little too quickly to be pools. The depth is in my opinion, not deep enough for marine life. Riffles are evenly distributed along the course of the creek, which is excellent. The main cause of riffles is big rocks jutting out from the surface of the water. In some places, the rocks are close to each other and create a large scale riffle. Some places have small scale waterfalls created by the difference in height of the creek bed. These also create riffles. Oxygen levels in the water are completely different from that in the air. The gills of the fish are much better at extracting oxygen than our lungs. Carbon dioxide dissolves into water more easily than oxygen does. Riffles aerate the water by passing the water through air. Water passing through air increases the area for oxygen to dissolve. Water that is at the bottom of the creek generally doesn’t have as much oxygen as the water located at the surface. Riffles provide the opportunity for the water to churn around. That way, the water will remain fresh and clean.

There are many signs of human impact on the First Creek. Although the bottom of the creek is not covered with concrete, as many rivers do in Japan, there are many other problems that may affect the creek ecosystem. The riparian zone of the First Creek has been greatly reduced due to the construction of houses and schools near it. Human impact is unavoidable in the modern age.

Assessment of the health of the riparian zone of the First Creek

There are several pools where aquatic creatures can live. There are many riffles even when the water level is high. There are no fish in the First Creek. However, having an oxygen-rich creek is beneficial for all plants and animals that live in and beside the creek. In summer when the temperature is high, the water’s oxygen levels will decrease rapidly. This leads to certain types of algae to bloom. When nutrients such as phosphates dissolve into the water in large amounts, algae grow and die quickly. The process of decaying consumes oxygen and oxygen levels decrease even further. Plants can use up a certain amount of nutrients but makes little or no difference to the ecosystem.

The riparian zone near our school is better than elsewhere. In some places, the creek is bordered by fences and squeezes its way in between houses. The banks of the creek in those places are only lightly covered by vegetation and native wildlife is rarely seen. Very little wildlife is seen outside our school as well. Some birds fly around and spend some time in the trees. The riparian verge has a lot of spaces and a person could easily go through them. This is not favourable for small animals that live on the ground. It doesn’t feel natural. It is like a man-made habitat that was created by copying natural habitats.Obviously any native wildlife would prefer undisturbed surroundings. If the riparian zone isn’t disturbed as much, animals may come back.

The bank vegetation of the First Creek is in a fair condition. It is not undisturbed as there are many large spaces in between trees and shrubs. There are some introduced plants around the First Creek close to the school.

There areprobably several Ash and Olive treesstill planted in areas not related to the school. I did not see any Ash or Olive trees during my investigation at school. The condition of the verge vegetation is poor. It is no longer than 2 metres in most places. There is some native vegetation distributed around the riparian verge.

The in-stream cover varies hugely between places along the creek. The area along the tennis courts has abundant cover. Other places are only slightly covered. Overhanging vegetation is fairly abundant along the school. Snags, logs and boulders are distributed extremely well in the First Creek along the school. A huge dead tree with its roots showing can be seen from the car park. There are several fallen logs. Boulders create well positioned riffles. Other places may not have so much cover. In-stream vegetation is a problem facing the First Creek. Most of the plants inside the water are likely to be not native.

The bank erosion and stability of the creek is poor. There is active erosion evident near the library/resource centre. It will eventually reach the school grounds. There are several bare banks which are bare because the plants that lived there were trampled on by school students. The plants most likely will die and new ones will not grow there unless someone plants some native species. Planting native species is one of the things that will help improve the riparian zone.

Riffles, pools and bends are virtually everywhere along the creek. The variation of habitats is good. The pools should be a bit deeper but will deepen as the water level rises. There are many bends. The depths of riffles vary. Aquatic life can be sustained quite well in the First Creek adjacent to the school.The only problem is that they have not come yet.