C19: Sustainable Urban Drainage Systems

Action C19 Sustainable Urban Drainage Systems will gain from action C2 sharing knowledge on CCA and rivers developed under different actions. Modelling, interpretations, analysis and data sampling are similar in the different catchments and C19 will benefit from this knowledge sharing. Scientific aspects currently the highly debated within EU, e.g. on the synergies and trade-offs between CCA and water ecology, the need for warning systems related to flooding of rivers and local contingency planning, and the synergies between farming and wetland restoration will also be shared and discussed for the benefit of action C19. Under Action C4 Rainwater, C19 will gain from the identification and experience of different setup models and testing of SUDS within CDR.

Under action C5 specific training courses, workshops and masterclasses, with point of departure in the challenges experienced by the partners will be implemented for the benefit of action C19 and other actions. Under action C6, the groundwater-surface water model and screening tool is developed and tested, and known warning systems in DK and in other countries are explored, and simple warning systems with flood prediction are tested and demonstrated, all activities which may benefit C19 directly.

Linked to Complementary Actions

As of now, no complementary projects are linked to C19

What

Samsø Municipality has a long history in engaging and activating local entrepreneurs in energy and climate aspects. By local entrepreneurship and community action SAK has obtained to implement solutions within renewable energy to an extent that it today is not only self-sufficient with renewable energy, it is delivering a surplus (cf. Table 2). For that reason, Samsø Municipality is famous as the “Energy Island” and attracts corporate tourists from all over the world.

The local Samsø spirit also affects how planning is carried out in other aspects than energy. In regard to Climate Change Adaption, Samsø Municipality wants to implement SUDS solutions with added value for biodiversity and of recreational use for the citizens. Often several meetings are held with interest groups, where the first meeting is held locally and the following meetings are held at the Island’s Energy Academy or at the City Hall.

In relation with Samsø Waste Water utility is to establish two retention ponds, Samsø Municipality and Samsø Waste Water Utility are in dialogue on alternative locations of the two ponds around Tranebjerg to accommodate both heavy rains and storm surges.

The East coast of Samsø lies at very low elevation, which results in flooding inland in situations of coupled events, whereas it is important to retain rain and surface water in SUDS.

Furthermore, establishment of new sewers at Tranebjerg, Langemark, Torup and Besser an opportunity arises to change the stream Sørenden from a drainage channel into a real watercourse. Sørenden have originally gone to Stavns Fjord, but to protect Stavns Fjord against pollution by nutrients and sewage, Sørenden’s water has been pumped to Kattegat via sea pipes since 1976.

The recovery of Sørenden also means that the restoration of Besser Made as a wet meadow area is possible. Such wetland will promote biodiversity with species such as geese, whooper swans and lapwings, which is linked to fresh meadow and marsh areas. If Besser Made subsequently nurtured by grazing, hay or other follow-up care, nutrient discharge to the sea will be reduced. In addition, there will be created even an attractive natural area on the island.

Protection of breeding birds and wildlife will have top priority, but in some places it is possible to meet the recreational needs of the construction of trails and shelters. The restoration of Besser Made is an important part of Samsø Municipality’s efforts in relation to the Natura 2000 area Stavns Fjord.

How

The action will include the following activities:

Phase 1: Year 2017-18

1. Analyses of alternative locations for the two retention ponds together with Samsø Waste Water Utility: incl. GIS, site analysis and hydraulic modelling using different climate scenarios.
2. Stakeholder and citizen involvement on the design of SUDS to create added value. Development of new methodologies for citizen involvement that are more network based. The stakeholder involvement will as a minimum include: Ballen Town and Harbour Forum, The Citizen Association, and The Boat Association.
3. Based on bullet 2 and 3, a conceptual design of the SUDS is developed and tender material is prepared.

Phase 2 and beyond:

1. Analyses of Tranebjerg, Samsø Golf Course, Besser Made and Ballen: incl. GIS, site analysis and hydraulic modelling using different climate scenarios. Moreover, additional sites are investigated to further retain water upstream.
2. Stakeholder and citizen involvement on the design of SUDS, recovery of Sørenden, restoration of Besser Made and recreational value. The stakeholder involvement will at least include: Samsø Golf Course, land owners and the Besser Made Association.
3. Based on activity 4 and 5, conceptual designs will be developed.

Where: Samsø Island

Figure 43: Map of Samsø Island

Phase 1
Activities 1-3
When: January 2017 – December 2018

Phase 2 and beyond
Activities 4-6

Retention of rainwater is necessary in situations where cloudbursts or long term heavy rains cause flooding in urban low laying areas. This situation combined with storm surge provides an even greater demand for rainwater retention upstream to delay surface water from the watercourse till the water level has decreased back to normal. This is especially important on Samsø, where urban areas are located in low elevation, near a watercourse and with short distances to the sea.

A general constraint is the fact that resources are short and not prioritized till a disaster has hit. In this case, traditional solutions are often chosen, and the opportunity of an integrated solution that also creates added value for the citizens is missed.

The added value is often what makes a project interesting for stakeholders and citizens, and an important parameter for a good involvement process and interesting outcome.

The involvement of the local community is essential for the success of the action. The many local projects established through Samsø’s Energy Island efforts were only realized because of the engagement of the local community and entrepreneurs.

Hydrologic modelling with different scenarios: zero-alternative, coupled events between heavy rains and storm surge, and climate scenarios provides background knowledge for the demands of the SUDS’ design.

Engagement of local stakeholders benefit with knowledge on locals’ use of the area and aspects that benefit added value for the local community.

Furthermore, conceptual designs for: SUDS at Tranebjerg, the area around Samsø Golf Course and Besser Made, rainwater retention and coupled events at Ballen will be made.

This results in a truly holistic CCA project combining usage of town and hinternland in an integrated solution, that also make nature restoration possible.

Expenses for external expert help is expected to amount to 7,000 € based on prior experience with external assistance to local projects.

Estimation of person days for Samsø Municipality is based on present salaries + pension etc. Samsø Municipality has ample experience with communication – also in cooperation with the Energy Academy.

C19

Phase 1:

• Technical background reports on site analyses and hydrologic modelling
• Report of conceptual design for the area around Samsø Golf Course and Besser Made.
• Documented stakeholder network methodology
• Report of conceptual designs for SUDS at Tranebjerg

Phase 2:

• Technical background reports on site analyses and hydrologic modelling
• Stakeholder involvement material and stakeholder input
• Report of conceptual design for rainwater retention and coupled events at Ballen
• Tender documents

General for Phase 1 and 2:

• Project video accessible at the C2C CC portal, at Samsø Municpality’s homepage (with LIFE logo).
• Documented press coverage in minimum 20 articles.

C19

Phase 1 
30/06/2017: Preliminary investigation and initial involvement of possible stakeholders done.
30/06/2017: Technical background report for modelling finalised.
31/12/2018:Hydraulic modelling incl. zero-alternative, coupled events and climate scenarios done.
30/06/2019: Conceptual Design for Samsø Golf Course and Besser Made finalised

Phase 2
30/06/2019: Preliminary investigations and initial stakeholder involvement done
30/06/2019: Technical background report for modelling finalised
30/06/2020: Hydraulic modelling incl. zero-alternative, coupled events and climate scenarios done.
31/12/2020: Conceptual Design finalised

31/12/2020: Tender material finalised