River Hazards and Opportunities

What are the causes of river hazards?

Rivers overflow their banks, leading to flooding, under two primary conditions:

1. Flash Floods: These occur after short bursts of intense rain. The land can’t absorb the deluge swiftly, leading to overland flow. Here, the water doesn’t infiltrate the ground quickly enough, and the river can’t disperse it fast enough.
2. Prolonged Rainfall: Continuous rain can saturate the soil and underground rocks. When additional rain falls, it cannot be absorbed and runs over the surface to the river, filling the channel.

These two conditions can converge in certain instances, resulting in particularly severe and dangerous floods.

Hazards from Rivers:

• Flooding: It can ruin crops and infrastructure and pose fatal risks to humans and animals.
• Disease Spread: Stagnant floodwaters can breed disease vectors. Mosquitoes, for instance, can transmit malaria and dengue. Contaminated waters can lead to cholera and diarrhoea.
• Population Vulnerability: Densely populated floodplains and deltas can make flooding perilous for vast numbers.
• Infrastructure Issues: The alluvial soil in floodplains and deltas isn’t stable for construction, demanding meticulous foundational work.
• Bridging Challenges: Erecting bridges over large rivers is costly and tricky, especially during floods. Many structures, unfortunately, get damaged, leading to bridge failures.
• Erosion: Swift rivers can erode their banks, endangering properties, infrastructure, and farmlands.

What are the opportunities of living on a floodplain, delta or near a river?

Despite the hazards, rivers, floodplains, and deltas offer several benefits:

1. Fertile Soils: Deposited alluvium during floods yields fertile lands, beneficial for agriculture, as seen with the Nile in Egypt.
2. Irrigation: River water aids in irrigating otherwise arid lands.
3. Transport Routes: Bigger rivers are key transport pathways, directly or via roads and railways built on their floodplains.
4. Food Source: Many rivers teem with fish.
5. Fresh Water Supply: They are crucial freshwater sources.
6. Development Potential: They offer expansive flat terrains suitable for housing and industrial development.