How To Talk About Low Impact Development

Stormwater engineers have always been involved in capturing rainwater and transferring it offsite as fast as possible. This approach managed to the construction of a vast operation of large, centralized processing facilities managing millions of gallons of stormwater annually – a very efficient, but not very environmentally-minded solution.

There has been a shift in the way we approach this problem. After decades of development that prioritized efficiency and convenience over sustainability, there is now a significant shift. Green Stormwater Infrastructure (GSI), a subset of low impact development solutions, is a method of stormwater management that mimics and/or restores the natural water cycle.

Image source google

GSI aims to reduce stormwater flow to large municipal systems, and the flooding and overflows that can be caused by their failures. Stormwater engineers trade pipe flow rates for soil/clay infiltration rates, and design methods that keep rainwater at the site, where it lands. This allows them to return rainfall to the natural environment after it has been cleaned.

This shift has a side effect: not all landowners and developers understand the benefits of green stormwater infrastructure. These systems' success depends on their design, maintenance, and education. To support architects and engineers designing them, site owners and developers need to understand and appreciate the value of these systems.

Low-impact development techniques have a positive impact on the environment, according to evidence ( GSI performance study). GSI encourages the use of infiltration and reduces hardscapes.

This results in less runoff from the surface, more pollution, lower erosion, and less flooding. Infiltration recharges the groundwater table and reduces urban runoff's impact on freshwater bodies (lakes, streams, oceans) and saltwater bodies. It also recharges base flows essential for fish and wildlife.

Grading Slopes Used In Land Development

A common feature of grading plan is the requirement that the engineer must adhere to the specified minimum and maximum slopes.

A common minimum slope for ground coverings such as lawns is one percent. This allows stormwater drainage. For safety reasons, a common maximum slope for grading design development is 25 percent. This means that there should be a one-foot vertical elevation difference over a four-foot horizontal distance change.

Image source google

A driveway's minimum and the maximum slope is one percent.

The plan might have labels for slopes that are proposed on it. These labels could be placed over specific areas or pointed to certain areas to make it clearer for someone who is using the plan.

A site grading plan can also include proposed spot grading.

Spot grades, also known as spot elevations, are points on a plan that have been marked with proposed elevations. These points can be used in areas that require additional grading details or clarification for the site contractor to determine where the proposed high and low points should be.

When designing a land development plan, civil engineers have a common goal: to create a site-grading design that balances.

Sites that balance are those that have a proposed site grade design that has earth cut that is equal to the earth fill amount. Sites that are balanced would not require extra earth to be removed from the site or imported into it.