The Kedron Brook

A field report experiment of The Kedron Brook on it's land features and transformations

List of Figures and Maps

1.0 Introduction

The Kedron Brook is a body of water flowing throughout the northern suburbs in South-east Queensland, extending from the D'Aguilar Range through to the Schultz Canal near Nudgee Beach. The Brook is important in housing ecosystems for an array of flora and fauna and important historical value to aboriginal people, the traditional custodians of the land. Over the past two decades an increase in populations along the Brook (which is 29 kilometres long) has altered the natural ecosystems to accommodate for local residents. Over these years of modifications there have been consequential ecological impacts on biodiversity and water quality of the stream banks. The biophysical process of erosion has geographically reshaped the natural landscape particularly for riparian zones surrounding the Brook. In the recent 2022 floods in South-east Queensland from February-March, the loss of riparian vegetation highlights the impacts of urbanization on infiltration, runoff and importance of soil profile on topsoil on the Kedron Brook

 

2.0 Methodology

The main primary data related fieldwork tests were conducted near Kedron State High School (Site A) and Nudgee Beach (Site B). These sites were investigated for quantitative measurements of certain properties of the Brook such as nitrate and phosphates levels, pH, turbidity and more. Although these results were mostly optimal, a qualitative assessment of the riparian vegetation cover for both sites were made to correlate with the potential sedimentation and increased erosion for the ecosystems. Two experts running the excursion from the Brisbane City Council also assisted in gaining qualitative data which became a focal point of the investigaton.

Secondary data in the form of reliable articles was acquired to substantiate the primary data and retrieving more qualitative data. This was required along with technological applications from ArcGIS to identify several other factors that may contribute to the erosion and damage for the ecosystem. It is also important to state that the recent February-March floods along with tidal influence from Nudgee Beach may have affected the data gained on site.

3.0 Land Transformations and Land Use

Riparian Vegetation Alterations and Impacts

Due to increasing land transformations to accommodate the growing population, heavy loss of riparian vegetation at the Brook's banks were observed in both Sites A and B. The loss of riparian vegetation in Site A is linked to the cement walkways and bikeways that are roughly three to four meters away from the stream bank. Moreover, from the observations on the extent of the riparian vegetation, it can be said that the vegetation cover has decreased due to the recent flood events. This can be seen on Map 1 comparing the extent of riparian vegetation during the fieldwork riparian assessment and a measure of what it was before. The assessment of Line A (during fieldwork observation) was estimated to be roughly to 1-2 meters long, whereas Line B (before flooding events) shows a length of approximately 2-3 meters.

Shown in figures 1A-1E; riparian vegetation loss in Site A shows large numbers of plants and sediments deposited across both sides of the stream banks. Erosion is prominent on this site due to several cement pathways being built beside the brook, which is seen on Map 2. Map 2 showcases several zones in Site A, specifically riparian zones, cement pathways and nearby communities. The pathways are located directly by the riparian zone and two residential areas located north-west and east of the zone

Additionally, A teacher parking facility located south of a pathway goes uphill towards Kedron State High School. With the surface of cement and replacement of natural soil for buildings and paths, infiltration of water into soil is prohibited. Hard and flat surfaces increase water velocity, therefore when large numbers of water flow downhill from the parking facility towards the riparian zone - sediments are displaced by the water and deposited elsewhere. Thus, the risk of floods being more frequent and impact increases/ The 2022 February Floods are a primary example of how runoff influences the sedimentation and erosion happening on the mid to lower end of the catchment (refer to figure 1A-1E).

Site B's riparian zone has less vegetation due to it being a beach. Despite this, there was still a significant impact on the soil profiles. This is seen in figure 2B, where several parts of land with sand have been washed away and deposited further down the catchment due to the lack of riparian vegetation holding it. East of Nudgee Beach where the Brisbane Airport is located, there is more presence of vegetation, trees and mangroves which anchor the soil together. As a result, the amount of erosion east of Site B is smaller.

Figure 3 - Runoff Rate Urbanization Comparison (Thamer et al., 2008)

With all factors mentioned above, the anthropogenic negative implications these will have on people (particularly in residential zones) will be increased vulnerability to floods. As seen on figure 3, runoff rates for areas after experiencing urbanization has bigger runoff rates whereas areas before experiencing urbanization have lower runoff rate. High runoff indicates faster flooding and therefore more erosion damage for the resident's land.

Water Quality and Species

Figure 4 - Water Quality Assessment

With so many constructions increasing runoff, there is also a rise in sedimentation and other natural processes occurring within Sites A and B that affect water quality.

Site A's nitrate levels and dissolved oxygen percentage were substandard (refer to figure 4), with roughly 5PPM for nitrates and an oxygen percentage of 23.3%, both of which are categorized as poor. Nitrate levels were poor likely due to the recent flood events that deposited sediments in the water from outside the riparian zones. Thus, nutrients may have been transferred. Dissolved oxygen percentages may be caused by nutrient levels fluctuating (as a result of the floods), causing algae to grow which consumes oxygen upon dying.

Another factor may be caused by the water temperature being at 27 degrees Celsius at the point of measurement. This is above average standards for freshwater bodies of water (2 - 26 degrees Celsius) (UCMP, 1996). Due to slightly higher temperature, dissolved oxygen in the water decreases with increasing solubility. Ultimately, these measurements were below conventional standards due to increased runoff from cement as the result of urbanization (therefore erosion).

Site B's brackish waters have similar results to Site A with the differences being salinity and turbidity. Dissolved oxygen saturation in site B is poor at 30.3%. This may be caused by temperature as during the time of measurement the water was 26.5 degrees Celsius which is a 2.5 difference from the average (Lakshmi, 2018). Due to high levels of salinity (ppm), dissolved oxygen and salinity have a similar effect to that of temperature, where solubility is the main factor. For turbidity, the additional erosion caused by floods and previous runoff affect the velocity flow of water in the brook (also affects sedimentation) which results in many sediments deposited down the catchment.

Worsened water quality has impacted native species whether invertebrate or vertebrate with specific environmental conditions considerably. With regards to poor water quality as a result of erosion and urbanization, many species with sensitive environmental conditions were not directly observed. Heavy floods (and its erosion damages) are also a factor for affecting sensitive species. Despite this, certain species at Site A are shown in figures 5A and 5B like freshwater tilapias which are adaptable and less sensitive to environmental changes. On the other hand, water striders are more vulnerable to changes in water quality. Aspects such as temperature, dissolved oxygen and nutrient levels were all relatively worse quality compared to Site B due to water runoff (refer to figure 4). Therefore, the species has less liveable habitat conditions and possibly endangered locally.

4.0 Evaluation and Recommendations

As a result of increasing populations in the Kedron suburb, subsequent land use changes have accelerated anthropogenic and biophysical processes, leaving significant impacts on natural ecosystems and native species. The issues of runoff and infiltration caused by construction and erosion from deficient soil profiles affect the environment such as their water quality. The 2022 February Floods highlights these issues as large portions of erosion along the riparian zones are due to reduced infiltration from nearby infrastructure. The riparian zone, another affected component plays a vital role in providing habitats for animal species.

Figure 6 - Lomandra (Longifolia) Species Variation

A solution introduced and disclosed by the Queensland Government to minimize the effects of runoff and infiltration are implementing more trees along the riparian zones (particularly around dense urban areas). An example similar plan conducted is the Queensland Government's North and Far North Queensland Monsoon Trough 2019, which seeks to recover riparian vegetation after suffering heavy droughts and subsequent floods. While it is ongoing since 2019, heavy progress has been made in reducing river and coastal erosion and increasing infiltration resilience (QRA, 2019). Regrowth of native plants are also a solution that is effective and not much of a disturbance to the ecosystem.

An example native plant viable for controlling erosion would be Lomandra Plants. Lomandras are used all throughout Australia (particularly Western Australia), specifically areas which are easily inundated. Lomandras have species variations which includes types suitable for wet river biomes in Queensland. This makes it popuilar for minimizing erosion and impacts of floods in riparian zones. The Lomandra Longifolia (refer to figure 6) is a type specifically used for controlling erosion, as it can increase soil stability by 366% due to its long roots underground (Ozbreed, 2022).

The effects these solutions have will mitigate the effects of erosion and other factors significantly. Human effects will also be reduced as a result of the effectiveness of trees and lomandra's soil stabilization.

5.0 Conclusion

Site A (Kedron) and Site B (Nudgee Beach) has undergone multiple biophysical and anthropogenic changes. Due to increasing populations, land transformations have impacted the runoff and infiltration of the areas which result in high risk of erosion and flood damages. Environmental impacts on flora and fauna species within the Brook were pointed out and assessed along with human impacts based on the water quality assessment for Site A and B in figure 4. Using this assessment along with secondary research, a recommendation for an effective solution was made to sustain riparian vegetation and minimize the impacts of erosion in order to increase water quality and liveability for residents.

6.0 Reference List

2.0

Australian Bureau of Statistics (n.d.). Data by region | Australian Bureau of Statistics. [online] dbr.abs.gov.au. Available at: https://dbr.abs.gov.au/region.html?lyr=sa2&rgn=302021031 [Accessed 10 May 2022].

3.0

Santhosh, L. (2018). Climate in a Freshwater Biome. [online] Sciencing. Available at: https://sciencing.com/climate-freshwater-biome-23959.html [Accessed 10 May 2022].

Rahman, M.L., Shahjahan, M. and Ahmed, N. (2021). Tilapia Farming in Bangladesh: Adaptation to Climate Change. Sustainability, 13(14), p.7657. doi:10.3390/su13147657.

National Wildlife Federation. (2018). Water Striders | National Wildlife Federation. [online] Available at: https://www.nwf.org/Educational-Resources/Wildlife-Guide/Invertebrates/Water-Striders [Accessed 10 May 2022].

Mohammed, T., Ghazali, A., Othman, S. and Sidek, L. (2008). Evaluation of XP-SWMM Sub-models in Predicting Flood for a Tropical Urban Catchment. [online] ResearchGate. Available at: https://www.researchgate.net/figure/Effects-of-urbanization-on-storm-runoff-Chow-et-al-1988_fig1_228835944 [Accessed 10 May 2022].

Queensland Government (2020). Tilapia. [online] Available at: https://www.daf.qld.gov.au/__data/assets/pdf_file/0009/1238076/tilapia.pdf [Accessed 10 May 2022].

ucmp.berkeley.edu. (2019). The freshwater biome. [online] Available at: https://ucmp.berkeley.edu/exhibits/biomes/freshwater.php#:~:text=Temperature%20varies%20in%20ponds%20and. [Accessed 15 May 2022].

4.0

Queensland;, c=AU; o=The S. of (2013). Preventing and managing erosion | Erosion. [online] www.qld.gov.au. Available at: https://www.qld.gov.au/environment/land/management/soil/erosion/management#:~:text=Surface%20cover%20and%20runoff.

Ozbreed Plants. (2021). Lomandras. [online] Available at: https://www.ozbreed.com.au/lomandras/ [Accessed 15 May 2022].

Queensland Government (n.d.). 2019 North and Far North Queensland Monsoon Trough | Queensland Reconstruction Authority. [online] www.qra.qld.gov.au. Available at: https://www.qra.qld.gov.au/recovery/recovery-operations/2019-north-and-far-north-queensland-monsoon-trough [Accessed 15 May 2022].

Queensland Reconstruction Authority (2019). North and Far North Queensland Monsoon Trough State Recovery Plan 2019-2021. [online] Available at: https://www.qra.qld.gov.au/sites/default/files/2020-03/north_and_far_north_queensland_monsoon_tugh_state_recovery_plan_2_1.pdf [Accessed 10 May 2022].

Figure 3 - Runoff Rate Urbanization Comparison (Thamer et al., 2008)

Figure 4 - Water Quality Assessment

Figure 6 - Lomandra (Longifolia) Species Variation