Sudden or progressive change in the environment adversely affects the lives or living conditions of people who may have been displaced from their origin. When environmental degradation occurs or sudden onset hazards impact vulnerable areas, people may be forced to move and relocate to areas that then require new infrastructure. The new infrastructure should be built to be resilient and strong enough to endure the impact of future natural hazards.

Excluded people hold the least power to influence decision-making whilst decisions regarding construction are usually made with people who hold significant relative power. Normally excluded people should be consulted regarding potential environmental impacts and regarding their personal needs and dependencies on the local environment.

Air pollution
Soil pollution
Water pollution
Eutrophication
Loss of biodiversity and ecosystems
Natural Resource Depletion
Soil erosion

Soil erosion and soil and water pollution caused by the construction of channels, and through inappropriate design and installation. Over compaction of soil, reducing surface water infiltration.

Blockage of migration routes and damage to breeding sites.

Potential injury to people or animals.

Construction of drainage channels can lead to a number of negative environmental impacts, and potentially some environmental improvements, depending on how well they are designed.

Soil erosion and soil and water pollution caused by the construction of channels and also by poor design and installation – channels that are too steep, or adjacent to uncovered ground can cause excessive soil loss. Unlined drainage channels (using soil as a surface) can also lead to soil erosion, particularly in areas of high slopes. They can also lead to the formation of stagnant water pools in flat grounds.

Over compaction of soil during construction, reducing surface water infiltration and therefore reducing groundwater recharge.

Unintentional blockage of migration routes and damage to breeding sites and potential injury to people or animals.

Map and model rain and surface water across the whole catchment; identify existing natural and human-made drainage; assess soil types and vegetation cover and natural infiltration. Determine the maximum slopes, spacing, appropriate location, and appropriate construction materials for drainage channels.

Installation of drainage can easily cause more problems than it solves. The only way to ensure drainage reduces flooding, waterlogging and stagnant standing water is to map and computer model rain and surface water across the whole catchment area. To do this, ground contour mapping, watercourses and springs should be identified along with existing natural and human-made drainage. Soil types and vegetation cover, bedrock, and natural infiltration should be mapped as well as agricultural activities that will increase or decrease surface water infiltration and soil loss. Determine the maximum slopes, spacing, appropriate location, and appropriate construction materials for drainage channels.

With the exception of fully saturated or impermeable soil (clay) or shallow impermeable bedrock, it is usually better to construct french drains or similar that help surface water to infiltrate the soil and replenish groundwater resources.

If the area is not modelled, any drains installed should be regularly inspected and monitored, and a budget set aside for modification and repair, to prevent negative environmental impacts from progressing. In instances where drainage is happening too quickly, it may be better to replace concrete channels with french drains.

Drains should be designed by drainage engineers, with appropriate slopes. Drains should be installed at shallow gradients that reduce the likelihood of soil loss.

Migration routes are often blocked by the clearing of trees to create construction or agricultural areas and by the construction of infrastructures such as roads, waterways airports, and rail. There are many examples from many countries where alternative routes around, under, or over infrastructure have been put in place, but most of these have failed or only worked in part. It is much more effective to map migration routes and plan activities to ensure they are not interrupted.

Percentage of linear meters of drainage channels that are properly design to avoid erosion or pollution events

Prevention of environmental damage

Mitigation of environmental damage

Time and resources and expertise to map and model drainage zones and design effective drainage that minimises negative environmental impacts and maximises groundwater recharge where the ground isn’t saturated or impermeable.