Essay Sample on Rivers: Dynamic Ecosystems from Headwaters to Mouth

Introduction

Rivers and streams change progressively, from headwaters to mouth, i.e., from steep, narrow, and turbulent flow to deep, wide, and meandering slow-flowing channels (Burk, 2018). Civil engineers have broadly evaluated the downstream pattern of rivers at different scales. Depth and width, longitudinal gradient, size of bed material, and velocity indicate interrelated changes. It is associated with variations in vegetal and animal communities. Rivers are considered as three-dimensional systems, including the vertical, longitudinal, and lateral dimensions across the river corridor (Burk, 2018). Rivers have been transformed for centuries to satisfy different social needs such as hydro-electric power production, navigation, checking erosion, and flood control. The changes have led to detrimental impacts on the environment, human interest, and resources. In the past decade, the problems have created a lot of management and public awareness, giving way to new objectives and conceptions in the field of civil engineering (Brierley & Fryirs, 2013). The main goal is to develop long term and sustainable management strategies. Most of the problems are directly or indirectly connected to changes in the geomorphological functioning of fluvial systems hence the need to integrate the geomorphological approach into river engineering practices (Alcayaga, Mao & Belleudy, 2018). This paper will investigate how sustainable long-term management strategies can be used to solve the impacts caused by river transformation to the ecology, human interest, and resources.

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Rationale

In many developed countries, reflective examination indicates the adverse effects caused by traditional river engineering practices, which have been gradually replaced by soft river maintenance practices where possible. River development has been there for centuries; however, it has increased dramatically in the past decade due to the rapid growth of economies. Environmentalists have created attention to show the detrimental effects of river rectification work in both rural and urban areas. A review of problems related to erosion management is, therefore, necessary to understand how river transformation is affecting the environment. For example, in the Rhone river basin, the flow is characterized by abundant bedload and high stream power, which are highly sensitive to disequilibrium in the sediment budget and any alterations inflow. In places where traditional policy has been disputed, soft techniques such as the use of vegetal structures have been applied as solutions to the issue instead of riprap protection. The use of natural structures rather than concrete ones is not part of the geomorphologic engineering approach. The approach is commonly referred to as mitigating engineering impacts through the use of alternative designs.

Geomorphological approach to river engineering applies alternative at the watershed scale and the reach scale based on a contemporary and traditional assessment of dynamics of geomorphology. Such strategies began receiving considerations in the Rhone basin in the early 1990s (Newson & Newson, 2000). The modern engineering geomorphology concept is dated back to the 1980s and has led to the conception that sediment transport and bank erosion are hydraulic risks (Newson & Newson, 2000). Ecological diversity, as well as deform diversity, should be preserved at the reach scale. Bedload sediments and transport continuity should, however, be maintained at the watershed scale. The adverse effects of traditional processes are evident in many high energy streams affected by disequilibrium in sediment and water flux. It is, therefore, essential to find alternative methods to mitigate these impacts and to promote sustainable gravel-bed river management. Geomorphic surveys conducted on rivers can be used to show how the sediment flux disequilibrium is affecting the environment and hence influence the river maintenance and control policies. It is necessary to present civil engineering principles to solve the geomorphic problems in rivers.

Approach

The approach used for this study will include identifying rivers in densely populated areas that have unstable streams. These are rivers described as 3rd to 8th order rivers mostly found in alluvial valleys (Gholami et al., 2019). The rivers selected have to be high energy streams (unit power exceed 100 Wm-2) and have gravel bedload and cobble (Gholami et al., 2019). Heavy rainfall and snowmelt affects the hydrology of the rivers. The next step will involve identifying the impacts or hazards caused by geomorphic and ecological changes. Many rivers have undergone channel metamorphosis, causing the prior braiding of waterways to be replaced by straight patterns and free meanders. The changes are due to the rapid changes in bedload supply and peak flows, entrenchment, aggradation, channel narrowing, and widening, which are recent characteristics of fluvial systems. The next step will involve picking case studies of rivers managing sediment budget at different scales.

A geomorphic survey will be conducted to identify the perspective of the geomorphology engineering approach with the concept that it is possible to reverse bed degradation by reactivating sediment supply through watershed management policies (DiazRedondo et al., 2017). The critical aspect of being considered should be the continuity of bedload transport along the full river course. This approach will assist in meeting and managing sediment deficit in rivers controlled by reservoirs.

Conclusion

In conclusion, a stream profile mirrors a balance between the size and volume of bed material on one hand and transport capacity on the other hand. In general, the upper part of rivers is mostly concave, and the discharge from upstream to downstream increases making bedload transport possible on the gentle slopes. Bedload size is also correlated to river slope, and the bedload size decreases downstream. Flux disequilibrium is a factor that causes most of the detrimental effects of traditional river engineering practices. It is, therefore, essential to mitigate these impacts by finding alternative strategies to promote sustainable river management.

References

Brierley, G. J., & Fryirs, K. A. (2013). Geomorphology and river management: applications of the river styles framework. John Wiley & Sons.

Thorne, C., Hey, R., & Newson, M. (2005). Applied fluvial geomorphology for river engineering and management. John Wiley and Sons Ltd.

Newson, M. D., & Newson, C. L. (2000). Geomorphology, ecology, and river channel habitat: mesoscale approaches to basin-scale challenges. Progress in Physical Geography, 24(2), 195-217.

Alcayaga, H. A., Mao, L., & Belleudy, P. (2018). Predicting the geomorphological responses of gravelbed rivers to flow and sediment source perturbations at the watershed scale: an application in an Alpine watershed. Earth Surface Processes and Landforms, 43(4), 894-908.

Stone, M. C., Byrne, C. F., & Morrison, R. R. (2017). Evaluating the impacts of hydrologic and geomorphic alterations on floodplain connectivity. Ecohydrology, 10(5), e1833.

Gholami, A., Bonakdari, H., Mohammadian, M., Zaji, A. H., & Gharabaghi, B. (2019). Assessment of geomorphological bank evolution of the alluvial threshold rivers based on entropy concept parameters. Hydrological Sciences Journal, 64(7), 856-872. Retrieved from https://www.tandfonline.com/doi/abs/10.1080/02626667.2019.1608995

Burk, T. (2018). Short-term Geomorphic Effects of Hofmann Dam Removal on the Des Plaines River by Tyler Burk, Bachelor of Civil Engineering (Doctoral dissertation, Southern Illinois University at Edwardsville).

DiazRedondo, M., Egger, G., Marchamalo, M., Hohensinner, S., & Dister, E. (2017). Benchmarking fluvial dynamics for processbased river restoration: The Upper Rhine River (1816-2014). River Research and Applications, 33(3), 403-414.