Managing ecological and climate risks

Moderator of this session: Jan Peter van der Hoek (Waternet)

This session will include the speakers: Ludolph Wetenholt (STOWA), Henk van Hardeveld (Waternet) and Sarpong Hammond Antwi (Centre for Freshwater and Environmental Studies, Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland)

Take a look at the abstracts below:

Living Lab Hedwige- Prosperpolder, a unique opportunity to develop flood resilience

Presenting author: Ludolph Wetenholt

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Partners from the Netherlands, Belgium, France and United Kingdom aim to enhance climate change resilience capacity. The overall objective of the Interreg 2Seas project Polder2Cs is to improve capacity to adapt to climate change through increased flood resilience, based on the demands of stakeholders and aimed at a strong overall societal embedding.

Depoldering of the Hedwige- and Prosperpolder offers a unique opportunity for a 6 km2 Living Lab at an operational levee, where innovative techniques, processes and products are tested for practical validation. First series of field experiments such as overflow tests have been performed in Winter and Spring 2021. Also, several emergency response exercises involving partners and observers were conducted. Innovative repair measures such as rock bags have been tested. A dedicated research and exercise program has been developed to be executed in the upcoming period.

To share results, we develop and offer a knowledge platform and expertise exchange. Basic versions of a Data wizard and Dijk Data Service Centre including research result so far are already available for project partners. Development and successful demonstration of the inspection instrument App2C has already interested organisations to further develop the app for broader use amongst professionals and the general public.

Both the results of the research programme as well as the joint exercises will support the development of flood resilience strategies, to be embedded in organizational and operational plans of stakeholders. Successful cooperation between national and regional authorities, universities and business has been established. We already brought together military and civil emergency organisations for joint working on emergency response. Action plans for prolonged collaboration are in preparation.

Key feature of the Living Lab is also to educate the next generation Water Managers. We contribute to academic curriculae and several Master and PhD students are actively working in the living lab on subjects concerning levee safety and emergency response. Furthermore, we educate and train young water professionals by involving them in field experiments and exercises. The first Winterschool for young water professionals and a Levee Challenge for student teams were great successes.

Designing water management strategies which minimize trade-offs between greenhouse gas emissions and flooding risks. 

Presenting author: Henk van Hardeveld

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The water systems of cities and their surrounding rural areas are often interwoven, which adds another layer of complexity to the challenge of designing adaptive and resilient water management strategies. In particular, cities in peatlands must face the challenge of how to minimize soil subsidence and greenhouse gas (GHG) emissions in the rural areas, without enlarging the impacts of flooding in the urban area. To contribute to our collective understanding how to deal with these conflicting goals, we examine the case of the Waardassackerpolder, a peatland polder of 15.7 km² just South of Amsterdam. The polder is shaped like a bathtub, with urban area with mean elevations ranging from +0.63 m to -0.72 m relative to datum, flanked by rural areas with mean elevations of 2.64–2.28 m below datum. 

We assessed the impacts of two water management strategies on soil subsidence, GHG emissions and flooding risks in the timeframe 2021–2051. The first strategy reflects the current policy, with surface water levels in the rural areas that are maintained at 76–103 cm below ground surface. The second strategy reflects a rewetting of the rural peatlands, with surface water levels raised to the ground surface. In both strategies, the surface water levels are periodically lowered to compensate for soil subsidence. First, we assessed the impacts of both strategies on soil subsidence and GHG emissions. Second, we used the resulting surface elevation models as input for an assessment of the time it takes before the first roads in the urban area are flooded, after the surrounding embankment of the rural areas is breeched. All assessments were made with the Tygron Geodesign Platform, with a resolution of 1 by 1 m.  

The cumulative soil subsidence of the current policy was 26.8 cm, which resulted in an emission of 24.9 t CO2-eq ha-1 y-1 and mean elevations of the rural areas of 2.91–2.50 m below datum in 2051. After the breech of the embankment, it took 35 hours before the first roads in the urban areas were flooded. The scenario with raised water levels resulted in 1.2 cm subsidence in 30 years (95% decrease) and a GHG emission of 8.9 t CO2-eq ha-1 y-1 (64% decrease). The mean elevations of the rural areas in 2051 were 2.66–2.29 m below datum. As a consequence, less water could be stored in the rural areas after the embankment was breeched. This resulted in a 21 hour window before the first urban roads were flooded. 

In this case, trade-offs between reducing GHG emissions and flooding risks were limited, i.e., 64% reduction of GHG emissions could be obtained with 40% less, but still enough time to safely evacuate the residents of the urban areas. In cases where trade-offs are more pronounced, we suggest designing water management strategies that result in slightly more soil subsidence in key rural areas, to allow for adequate evacuation times in urban areas. The Tygron Geodesign Platform can be used for integrated impact assessments that can support such design challenges. 

Communicating climate risk in the water sector: A case study of the 2018 and 2020 drought events in the Republic of Ireland. 

Presenting author: Sarpong Hammond Antwi (Centre for Freshwater and Environmental Studies, Dundalk Institute of Technology, Dundalk, Co. Louth, Ireland)

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The prevalence and impact of drought has become a growing concern due to its socio-economic, environmental, and health impacts, continuously changing the narrative across different climatic zones. Historical reconstructions indicate that the Republic of Ireland – as a wet country, has experience over 45 droughts events since 1850. The drought events of 2018 and 2020 left a significant impact on water availability and supply, leading to changes in water sector management and policies, including a water conservation ban. However, the national utility’s communication approach, public perception of water resources availability, and the level of knowledge and awareness on factors that jointly influence water supply such as over-abstraction, climate change, and the extent of media attention have been influencing water conservation efforts and measures particularly during periods of drought. Using sentiment analyses (SA) of social media communication (Facebook and Twitter), newspaper coverage of drought, and stakeholder interviews, our study aimed to catalogue communication lessons from the two drought events of 2018 and 2020 and propose options to enhance public communication on water resource availability in the Republic of Ireland. Our findings revealed that despite accessible portals providing data and information on water resources, no comprehensive National Drought Information Management System nor national drought policy plan was available as prevailing in many drought-prone countries. Dialogical communication between the national utility company and the public was also limited, while newspaper coverage of drought events changed significantly in 2018 and 2020. Newspaper reports were also framed on uncertainty and risk (41% n=71), which had implications on public support and engagement for water conservation actions instead of stimulating it. Based on our findings, we demonstrated the need for public engagement, multi-sectoral interest and collaborative efforts to communicate drought and water conservation measures. Recommendations made in this study also aim to provide information for effective message development and delivery that could be constructive for water utilities, the media and other water sector organizations as they develop risk communication plans, particularly on drought.   

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