How does urbanization typically affect river systems?

Urbanization typically has significant impacts on river systems, primarily because it alters the natural landscape and hydrology. As cities expand, vegetation is removed, and impervious surfaces like roads and buildings increase, which disrupt the natural flow of water. This alteration leads to increased water runoff, as rainfall and melting snow do not have the opportunity to percolate into the ground but instead flow directly into rivers.

Furthermore, urban areas tend to introduce a variety of pollutants, including chemicals from vehicles, oils, and waste materials, into the river systems. As the surfaces become impermeable, the likelihood of these contaminants reaching waterways significantly rises, leading to poorer water quality. This combination of increased runoff and pollution can severely impact the health of river ecosystems and the organisms that inhabit them.

In contrast, other effects such as decreased water temperature, promotion of biodiversity, or reduction of sediment flow do not directly align with the typical consequences of urbanization. For instance, while it could be argued that some urban areas might incorporate parks that mitigate temperature, the overall trend in urbanized environments shows an increase in water temperature due to runoff from heated surfaces. Similarly, urbanization tends to negatively affect biodiversity due to habitat destruction, rather than promoting it. Lastly, sediment flow may be altered,