Environmental Impacts of Flooding
Flooding can have a variety of direct impacts on the environment and ecosystems contained within a flooded region. Some of these impacts are positive; flooding is a natural ecological process that plays an integral role in ensuring biological productivity and diversity in the flood plain. Other impacts of flooding may be less positive, and in some cases can result in environmental degradation. The most extensive and difficult to repair environmental damage usually occurs in developed areas located in the floodplain.
Flooding can directly impact: the health and wellbeing of wildlife and livestock; riverbank erosion and sedimentation; the dispersal of nutrients and pollutants; surface and groundwater supplies; and local landscapes and habitats.
Wildlife and Livestock Health and Well-being
Flooding can affect the health and well-being of wildlife and livestock. Large quantities of water can negatively affect natural and ranching and farming habitats. For example, after the 2011 Queensland, Australia floods, thousands of animals died as a result of water inundating their habitats. Furthermore, livestock unable to relocate to higher ground in time were washed away by flood waters or forced to stand in polluted water until rescued.
If a flood is large enough, it can result in a loss of wildlife and biodiversity in the flooded region. This may reduce the level of biodiversity, habitat potential and food present in the ecosystem, creating long-term impacts for surviving wildlife.
Riverbank Erosion and Sedimentation
Riverbank erosion is caused by high and fast moving water that exceeds riverbanks. The impact of riverbank erosion is most felt in developed areas.
Sediment may act as a form of non-point source water pollution that can clog riverbeds and streams as well as reduce storage capacity for reservoirs and wetlands. Flood waters can carry large amounts of sediment and leave deposits behind once flood waters recede. If extreme enough, sedimentation can degrade water quality and temporarily affect municipal, industrial and recreational water supply.
Dispersal of Nutrients and Pollution
Flood water can contain debris, pollutants and nutrients. Debris can include trees and stones, or even pieces of houses. Pollutants in flood water, such as bacteria and pesticides, can be carried far distances. Sedimentation and turbidity can result in the growth of algae and phytoplankton blooms that jeopardize water quality.
Important nutrients and mineral deposits can also be dispersed by flood water, resulting in improved plant growth and overall ecosystem health. Over time, the nutrients, organic material and sediment carried by flood waters and deposited on the landscape can provide fertility benefits.
Replenishment of Surface and Groundwater
One of the positive direct benefits of flooding is the replenishment of surface water and groundwater supplies. The replenishment of supplies can benefit soil, resulting in healthy crops and pastures.
Local Landscape and Habitat
Flooding can change local landscapes and habitats. For example, John Pomeroy, a professor and water researcher at the University of Saskatchewan, explained that the 2013 Alberta floods changed the Rocky Mountains and foothills region, thus altering everything from how future floods will play out to how animals will build habitats in these regions.
In urban areas, flooding can be extremely damaging and costly, as it can negatively impact infrastructure, homes and businesses. In the natural environment, however, flooding has a more positive impact on the natural environment as flood water provides nourishment to the landscape.
 “Environmental Aspects of Integrated Flood Management.” Associated Programme on Flood Management. WMO. Published August 2006 in Geneva, Switzerland. Pg. 34
 Dumas, Daisy. ( 2011, January 14). Wildlife hit hard by Queensland floods. Australian Geographic. Retrieved from http://www.australiangeographic.com.au/news/2011/01/wildlife-hit-hard-by-queensland-floods/
 Stream Notes. (n.d). Soil in our Streams, 1(1). Retrieved from http://www.bae.ncsu.edu/programs/extension/wqg/sri/sediment5.pdf