At the stakeholder consultation workshop, three urban EbA measures were identified and selected to pilot in Dong Hoi city, including:
1) The water retention measure aims to address flood risk through water retention and delayed runoff during flooding, and heat stress reduction in the core urban zone of Dong Hoi City. It integrates urban flood risk management, relieves pressure on Cau Rao River as the main floodway protecting the city, improves existing ecosystem health, and increases blue-green space for the city. The measure is designed with multiple urban EbA components, including (1) a water retention area for flood reduction, (2) permeable surfaces (e.g. grass, vegetation and pavement) for storing water runoff, (3) swales along the existing road to reduce runoff and infiltration of pollutants, (4) additional trees to provide shading and regulate microclimate, (5) a protected area for habitat and to enable scientific investigation.
2) The green wall and green roof measure aims to conserve green spaces in the municipality in the face of increasing pressure to develop the natural lands due to rapid urbanisation, contribute to the reduction of surface temperature and heat stress during hot summer months and flood risk mitigation, green-blue components (e.g. trees, vegetation layers...). The measure is designed with facade greening on exterior walls and a rooftop garden replaced the traditional corrugated iron-roof of the building adjacent to a rainwater harvesting system.
3) The Sustainable Urban Drainage System (SUDS) aims to enhance the drainage system through applying a nature-based approach in the construction and operation of the system to improve the flood management in the urban area. It helps to address the problem of local hotspot flooded areas during heavy rainfalls or typhoons in Dong Hoi city. The measure is designed and implemented with following components:
- Two underground storage tanks with storage capacity of 150 m3 with soak-away structure
- Eight inlets to collect rainwater on the road surface around the site
- Perforated uPVC collection pipes that are connected to the existing drainage system with a one-way backflow preventer
- Sidewalk paving slabs replaced by permeable structure
- Green trees to increase water permeability on land surface
The results showcase the effectiveness and possibilities of green interventions in helping the city to cope with increasing temperatures, flood management and energy efficiency while reducing GHG emissions. On top of that, lessons learnt and practical experiences in terms of technical knowledge, methodology and approach were shared, expanded and integrated into provincial technical standards, urban planning and relevant binding documents.
In fact, in order to finalise the urban EbA measures at site after the selection process, there were different steps required according to Viet Nam's legal frameworks and project's procedures:
- Site assessment: Planning an urban EbA measure required a thorough site assessment of the local climatic and geographical conditions to inform the optimum design and installation requirements. A comprehensive site assessment examined climate, hydrology, soil and water conditions on meso- and micro-level and takes into account the existing built environment.
- Planning: At this step, it was important to set an upfront goal of each urban EbA measure as this will influence the design, construction and level of maintenance required for the system. The scale, relationship to other facilities, benefits and impacts to communities and region, problems to be addressed were defined and elaborated. In addition, stakeholder engagement needed to be considered to define relevant involved parties and their roles, specialists, technical designers and service providers. All relevant procedures and regulations were figured out as well.
- Design phase: The crucial step of this phase was to develop a technical design document for the measure. Based on the set goals, site assessment results and requirements, the designers and technical experts prepared the technical drawings and the design report. Aspects related to size, functional components, technology, materials, timeline and cost estimation needed to be included. Consultation process to present the technical design was conducted for comments and feedback from different stakeholders before submitting all files for approval by local authorities. Upon the approval of the technical design document, the process to obtain the construction permit needed to be carried out according to government regulations.
- Implementation: The construction implementer and construction supervision consultants were selected through a bidding process. An implementation plan was worked out and agreed by all relevant stakeholders before construction on the site. Local authorities and project partners took the roles of overall management, monitoring the work progress. Monthly meetings were conducted to update the progress and deal with arising issues during the implementation. The relevant government regulations and standard requirements needed to be complied fully and strictly at this phase. At the end of this phase, the implementation guidelines, lesson learnt and leaflets to promote the results were developed and shared in public for awareness raising and upscaling in the region.
- Maintenance: Upon the completion of the implementation phase, the urban EbA measures were handed over to provincial partners. A consultation process was conducted to agree upon the roles and responsibilities on management, operation and maintenance of the work by parties who took over. Planning and budget allocation was prepared and committed to on the partner side.