Question

The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. What human activities tend to increase flood risk? (E)

Short answer

Human activities increasing flood risk include deforestation and land clearing, urbanization, altering river courses and floodplain development, contributing to climate change, and implementing inadequate drainage systems. Deforestation reduces the land's capacity to absorb water, leading to rapid runoff. Urbanization involves creating impervious surfaces that don't absorb water, causing increased water flow into rivers. Alteration of river courses can inadvertently increase flooding in certain areas, while building on floodplains obstructs natural water flow. Climate change due to human activities like burning fossil fuels can lead to extreme weather events and increased flood occurrence. Lastly, poorly designed and maintained drainage systems in cities can lead to flooding.

Step-by-step solution

Deforestation and Land Clearing

One human activity that increases flood risk is deforestation and land clearing. When trees and vegetation are removed from an area, the ground becomes less capable of absorbing water. This causes rainfall to run off the surface more quickly, which leads to more water rushing into rivers, thus increasing the risk of flooding.

Urbanization and impervious surfaces

Another human activity that can increase flood risk is urbanization and the creation of impervious surfaces, such as roads, parking lots, and buildings. These surfaces prevent water from being absorbed into the ground, causing more water to flow into rivers and streams, increasing the risk of flooding.

Altering river courses and floodplain development

Another factor contributing to increased flood risk is altering river courses and floodplain development. Humans often modify river courses to suit their needs, like for agriculture or to prevent flooding in certain areas. However, this can cause the river to flood more easily in other areas. Building on floodplains can also increase flood risk, as these areas are naturally prone to flooding, and human infrastructure can obstruct natural water flow.

Climate change and sea level rise

Climate change caused by human activities, such as burning fossil fuels and deforestation, can contribute to increased flood risk. This is because climate change can lead to more extreme weather events, which in turn can result in more intense rainfall and flooding. Additionally, sea level rise caused by melting ice caps and glaciers can increase the risk of coastal flooding.

Inadequate drainage systems

Lastly, another human activity that can increase flood risk is the implementation of inadequate drainage systems. In urban areas, if stormwater drainage systems are not effectively designed and maintained, the excess water can overwhelm the system and lead to flooding in surrounding areas. Proper management of drainage systems is crucial for preventing floods. In conclusion, human activities such as deforestation, urbanization, river course alteration, climate change, and inadequate drainage systems all contribute to increased flood risk. It's essential to consider the impacts of these activities and implement measures to reduce the risk of flooding.

Key concepts

Deforestation and Land Clearing

The removal of forests and vegetation has a direct impact on local ecosystems and their ability to manage rainfall. Trees and plants play a crucial role in the water cycle by absorbing rainfall and slowly releasing it back into the atmosphere through transpiration. Without vegetation, water flows quickly across the soil surface, leading to runoff that can accumulate and overpower rivers and streams, causing floods.

Furthermore, roots of trees and plants help to hold the soil together, preventing erosion. When these roots are removed, the eroded soil can clog waterways, which exacerbates flooding. To mitigate these effects, reforestation and sustainable land management practices are essential.

Urbanization and Impervious Surfaces

As cities grow, the construction of buildings, roads, and other infrastructure creates impervious surfaces that do not allow water to soak into the ground. Instead of being absorbed, water runs off these surfaces quickly, leading to increased volumes and speed of water flowing into stormwater systems and local water bodies.

Impervious surfaces are a significant factor in urban flooding, and solutions to this problem might include green infrastructure such as green roofs, rain gardens, and permeable pavements which can help absorb and manage the water more effectively.

Altering River Courses

Human intervention in natural river systems—whether for agriculture, development, or flood prevention—can have unintended consequences. Changes to a river's course can disrupt its natural flow, often leading to increased flood risk downstream.

River engineering and the development of floodplains should consider historical flood patterns and should incorporate flood control measures that work with, rather than against, natural river dynamics. Restoring meanders and floodplains can be an effective flood mitigation strategy.

Climate Change and Flooding

Climate change, driven by human activities like burning fossil fuels and deforestation, intensifies the water cycle, leading to more extreme weather events, including heavy rainfall and flooding. An increase in the frequency and severity of storms can result in rivers and drainage systems becoming overwhelmed.

To reduce flood risks associated with climate change, actions such as cutting carbon emissions, enhancing natural flood defenses, and planning for more extreme weather events are critical.

Inadequate Drainage Systems

In urban environments, the effectiveness of drainage systems is paramount in preventing floods. Without proper design and maintenance, drainage systems can quickly become overburdened during heavy rains, leading to floods. It is essential that urban planners and engineers design adequate drainage infrastructure that can handle the expected influx of water from increased impervious surfaces and extreme weather events.

Regular maintenance and updates to existing drainage systems, as well as innovative solutions like stormwater retention ponds and bioswales, can help manage excess water and reduce the risk of flooding.