Development can have a significant impact on stormwater drainage in an area. The quantity of land available for water to infiltrate into the soil is decreased when natural surfaces like bare ground or grass land are converted to impermeable surfaces like highways, buildings, and parking lots. This can lead to higher runoff during rain events. Flooding, erosion, and property and infrastructure damage may result from this.
Additionally, because development alters the hydrological regime also known as amount and speed of water flowing, it may have an impact on downstream flooding. The amount and speed of water flowing into streams and rivers thus rises along due to increased runoff. As a result, flooding may occur downstream of the built region and stream flows may increase.
Downstream flooding can also be largely caused by the decrease in floodplain storage capacity as a result of development. Natural floodplains have the capacity to temporarily store floodwaters, minimising their effects downstream. Development in flood-prone areas, however, may result in the loss of these natural floodplain storage areas, reducing their capacity to lessen the effects of downstream flooding.
Stormwater management techniques like low-impact development, green infrastructure, and various types of stormwater detention ponds can be used to mitigate these effects. Through encouraging infiltration, evapotranspiration, and the natural treatment of stormwater runoff, these measures work to control the volume and velocity of runoff. By limiting direct runoff of stormwater, these strategies can reduce the likelihood of infrastructure and property damage both locally and further downstream. It can also help in prevent flooding, and protect water quality.
Increased development without mitigation measures can cause flooding in the downstream areas as we have witnessed recently during several events in Pakistan.
ESSENTIAL STEPS TO CARRY OUT STORM WATER ANALYSIS
Before carrying out stormwater analysis, it is essential to collect baseline data on the existing conditions in the area. This data can be used to assess the potential impacts of development on stormwater runoff and design appropriate stormwater management strategies.
The following are the steps to carry out stormwater analysis before and after development:
1. Collect existing data:
Collect existing data on the area such as topography, land use, soil type, vegetation cover, hydrology, and climate.
