How do you design a low-impact development strategy for stormwater management?

Assessing site conditions is crucial. Each site presents unique challenges and opportunities. Soil tests unveil absorption capacities, guiding decisions on infiltration systems. Similarly, mapping drainage areas aids in pinpointing potential runoff hotspots. By meticulously analyzing these factors, a tailored LID strategy can be crafted to manage stormwater while harmonizing with the environment effectively.

1 - Assessment and Planning 2 - Topography, Soil Analysis, Hydrology 3 - Setting Goals and Objectives 4 - Runoff Volume Reduction 5 - Flood Control 6 - Ecosystem Protection 7 - Design Principles 8 - Minimize Impervious Surfaces 9 - Preserve Natural Features 10 - Reduce Pavement 11 - Green Roofs 12 - Vegetated Buffers 13 - Natural Drainage 14 - Bioretention Systems 15 - Permeable Surfaces 16 - Rainwater Harvesting 17 - Bioswales 18 - Designing Specific LID Practices 19 - Integrating LID Practices into the Site 20 - Construction and Implementation 21 - Maintenance and Monitoring 22 - Community Engagement and Education 23 - Best Management Practices (BMPs) 24 - Rain Gardens 25 - Local Codes and Ordinances 26 - Permits and Approvals

Assessing site conditions and constraints is foundational for successful implementation of Low Impact Development (LID) practices. Utilizing tools like maps, surveys, and hydrologic models to gather data helps identify opportunities and challenges. Understanding factors such as soil type, slope, land use, and regulatory requirements is essential for effective planning and design of LID strategies tailored to the site's specific characteristics. This thorough assessment ensures informed decision-making and optimized outcomes in sustainable stormwater management.

I agree, however, I believe site assessment can be classified into more comprehensive steps including hydrologic, hydraulic, geotechnical, topographic, and land use criteria. It helps to cover more technical aspects and details in site study step. I think more detailed study in this step leads to better decision about the type and arrangement of LID practices and reduces the extra costs in the implementation step.

In addition to this point, incorporating the perspective of human and community acceptance is a crucial aspect of site assessment, especially when implementing Low Impact Development (LID) practices. It's great that you are considering not only the technical aspects like soil type and drainage but also the social aspects.

Defining clear goals and objectives for your Low Impact Development (LID) strategy is essential for its effectiveness. Goals such as reducing runoff, improving water quality, enhancing aesthetics, creating habitat, and saving costs provide a focused direction. Using performance criteria like runoff reduction and water quality treatment helps quantify these goals, ensuring measurable outcomes. Incorporating stakeholder preferences and feedback ensures alignment with community needs and expectations, fostering support and sustainability for LID initiatives.

For effective stormwater management, the second step in crafting an effective Low Impact Development (LID) strategy is to meticulously define your goals and objectives. These objectives serve as the guiding stars, steering your efforts towards tangible outcomes that benefit both the environment and your bottom line. Your goals may encompass a spectrum of aims, from curbing runoff volume and mitigating peak flow to elevating water quality standards, enhancing the visual appeal of landscapes, fostering habitat creation, and even trimming operational costs. Each goal represents a vital piece of the puzzle, contributing to a holistic approach to sustainable stormwater management.

In my belief, enhancing aesthetic is not a goal, but a criteria to be considered during design step. Moreover, to define the main goal of a LID practice, it is necessary to express the principles of the LID practice including conserve natural areas, minimize development impacts, maintain site runoff rate and control small storms.

This is very important,, In Pakistan we have been wasting the excessive natural water supply in form of flood and storm water mainly due to lack of defining the objective of the system that should be needed

By clearly defining goals and objectives, such as reducing runoff volume and peak flow, improving water quality, and considering factors like aesthetics and habitat creation, you set a clear direction for your LID strategy. Using performance criteria to quantify these goals allows for objective measurement of success and ensures that LID practices are designed to meet specific targets. Additionally, considering stakeholder preferences and feedback ensures that the LID strategy is responsive to the needs and expectations of those involved, promoting stakeholder buy-in and support throughout the process.

By categorizing LID practices into source control, conveyance control, and end-of-pipe control, you can systematically evaluate options based on their suitability for your specific circumstances. Source control practices target runoff at its origin, while conveyance control slows and treats runoff along its path, and end-of-pipe control manages runoff before discharge. This classification helps in identifying the most appropriate practices for addressing specific challenges and achieving desired outcomes, ensuring a holistic and effective LID strategy.

In my past projects I have used LID design manuals from federal organizations like the U.S. Environmental Protection Agency (EPA) or local authorities that have jurisdiction (AHJ) We had a professional engineer (PE) and a landscape architect experienced in LID design for complex projects these additional resources helped the success of the project.

Selon moi, afin d'éviter au maximum le ruissellement, et le chargement en pollutions au cours de ce ruissellement, il convient de chercher à minimiser la longueur sur laquelle l'eau va ruisseler.

Choose LID practices that align with the site conditions and goals. Options include rain gardens, permeable pavements, green roofs, and bioswales. These practices aim to mimic natural water cycles, promoting infiltration and water quality improvement.

Green streets incorporate various LID practices to manage stormwater while enhancing urban aesthetics. In a redevelopment project in Leeds, we designed green streets with permeable pavements, street trees, and bioretention cells. Street trees were selected based on their canopy coverage & root system structure to maximise stormwater interception and infiltration. Bioretention cells were integrated into curb extensions to treat roadway runoff. Providing training on urban forestry, tree species selection, and integrated stormwater management practices is essential for designing successful green street initiatives Underground detention systems temporarily store stormwater and release it at a controlled rate, reducing peak runoff

By focusing on details such as size, shape, location, materials, and maintenance requirements, you ensure that each LID practice is tailored to the site's specific conditions and objectives. Utilizing design manuals, guidelines, and standards helps adhere to best practices and ensures compliance with industry specifications. Additionally, leveraging design software allows for precise modeling and optimization of LID practice performance and cost-effectiveness. This comprehensive approach enhances the functionality and efficiency of LID strategies, ultimately maximizing their benefits for water management and environmental sustainability.

Another software I have used in the past for low impact drainage design studies is PCSWMM. Once model is calibrated with topographical and other pertinent information, we can introduce LID practices into the model and simulate their impact on stormwater runoff characteristics. PCSWMM allows you to model various LID practices simultaneously and assess them before implementing. I was able to check for our LIDs effectiveness in reducing runoff volume, and in improving water quality of the net process.

Design each chosen LID practice with site-specific factors in mind. For example, determine the size of rain gardens based on anticipated stormwater volumes or calculate the permeable pavement depth needed for proper infiltration. Ensure the design supports both functionality and aesthetic value.

From site preparation to practice installation and inspection, attention to detail is key to ensuring quality and compliance. Utilizing tools like checklists, contracts, and permits helps maintain standards throughout the implementation process. Moreover, engaging stakeholders through training, education, and outreach fosters understanding and buy-in, promoting the long-term success and sustainability of LID practices. Overall, this step emphasizes the importance of proactive management and communication to realize the full potential of LID strategies.

In my opinion, the training of local resources to maintain the LID is of paramount importance. These individuals understand and have skin in the game. Their families are directly or indirectly affected by the work they sign up to do for the success of the LID. Finally it would be wise to document all the goals, the steps taken to achieve the goal, and the training provided to potential employees and the community at large. Any LID has multi-generational impacts and one generation may not pass everything they learned from your team by words and training to the next. Your documentation will help the success of your LID in the next generations.

Put the design into action by working with qualified contractors and stakeholders. Effective communication during implementation helps to ensure the project meets design specifications and remains on track in terms of budget and timelines.

Monitoring and evaluating the performance over time provides valuable insights into how well the practices are functioning and whether adjustments are needed. By collecting data on various parameters like runoff quantity and quality, soil moisture, and plant health, you gain a comprehensive understanding of the effectiveness of LID measures. Leveraging instruments such as rain gauges and water quality sensors facilitates accurate data collection, while methods like visual inspection and stakeholder feedback help assess satisfaction and identify areas for improvement. Overall, this step emphasizes the importance of continuous assessment and refinement to enhance the long-term impact of LID strategies.

We are engineers, to document with stats and data should be our primary goal in any project let alone a multi-generational project like a LID. Regular testing by trained individuals for the first six months of operation is wise. After this period of regular testing, the testing frequency may be reduced and the data collected during these tests can be used to check against the model values and the values collected in the first six months. If the data seems to be trending away from the design conditions over time, reevaluating the design and the data would be wise to ensure that the LOD can be steered back to achieve its initial design goals.

Post-construction, monitor the effectiveness of the LID practices. Measure outcomes like runoff reduction, water quality improvements, and ecosystem health. Regular evaluations allow for adjustments and optimization over time.

In a recent urban redevelopment project, we integrated a comprehensive low-impact development strategy to address stormwater management challenges while revitalizing the community. By engaging local residents through workshops & informational sessions, we nurtured a sense of ownership & stewardship among community members, leading to widespread support for the project. The inclusion of permeable surfaces, rainwater harvesting systems & extensive green infrastructure not only reduced stormwater runoff but also enhanced the overall livability of the neighborhood. Ongoing collaboration with regulatory agencies & active involvement of maintenance teams ensured the long-term success & sustainability of the stormwater management approach

Consider exceedance. The system design will be exceeded at some point, either because of extreme rainfall or because of operational problems. You need to consider what happens to the runoff when that happens. This needs to be considered at each step starting with the site assessment.

Excellent recommendation by Martin Osborne to evaluate a low-impact development strategy for stormwater management both for hydraulics for the typical design storm and for the reliance during the events that exceed the design storm. To have a successful low-impact development strategy for stormwater management, it has to perform as expected during normal design conditions and to at least cause no harm during extreme events.

In my past projects that deal with water rain-off we solicit inputs from local communities that have dealt with such extreme events in the past. Most times, there may be a older person in the community that share stories of what his/her generation did in the past or, what their forefathers did to help. Most times those stores are based on past tests done by that generation and it would be wise to not reinvent the wheel but, build upon the basis of what has worked for that area in the past.