Building with Nature Indonesia, Securing Eroding Delta Coastlines - Design and Engineering Plan

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This design and engineering plan is produced during the inception phase (result 1) of the project and should be understood as a preparation for result 2 in which we aim to implement a large scale demonstration project in Demak. As such, this plan provides the concepts, reasoning, design and practicalities for the timely implementation of Building with Nature measures in Demak district. It sets priorities and sequence of implementation, and addresses limitations and risks, which will be accounted for and resolved in an adaptive approach. Next to these practical aspects this report also aims to serve as input for fruitful stakeholder engagement at the community, district, provincial and national level (result 3 and result 5) and for the Environmental Impact Assessment (result 1.11).

As demonstrated in the system analysis (Chapter 2), a lack of coastal safety is currently severely hampering socio‐economic activity in Demak´s coastal zone. Conventional hard‐infrastructure solutions to enhance coastal safety have been found to be ineffective, expensive and unable to adapt to climate change in soft muddy coasts. Furthermore, they fail to bring back the economic, environmental and social benefits that healthy mangrove coastlines could offer. A more holistic and long term solution like Building with Nature is needed that addresses both the root causes of the problem, while taking into account the economic and social well‐being of the inhabitants. In line with this reasoning, we envision:

A safe and prosperous Demak district, in which a mangrove greenbelt provides the coastal safety and resilience needed for the communities to thrive such that in turn they can sustain the mangrove greenbelt they rely on.

As a project, we will help to realize this Master Plan vision by implementing measures that are specifically designed to trigger change at a larger scale by other actors. In line with the vision statement for Demak´s coastal zone as presented above, the (narrower) local project objective reads:

A large‐scale implementation of the Building with Nature approach halts coastal erosion along a 20 km shoreline and triggers revitalization of 6000 ha of degraded aquaculture ponds in Demak district.

The vision statement implies that coastal safety measures need to be intricately linked to socio‐economic measures. That is why we choose to implement such measures by introducing the Bio‐Rights approach. Further, we explained that the Building with Nature approach is inherently an adaptive approach. First because it is a participative approach that needs various rounds of consultation especially with local communities. Secondly, because we need to 'learn by doing´ and enhance our system understanding along the way. This is why we choose to facilitate the implementation of measures in Demak with Coastal Field Schools.

Building with Nature solutions come in many different forms and shapes. Chapter 4 presents a range of potential coastal safety measures and socio‐economic measures that may be applicable in Demak’s coastal zone and elsewhere in Northern Java. In Chapter 5 we present the spatial project design in which we elaborate which combination of measures we propose in the three coastal zones of Demak to achieve our vision. To determine the right combination of measures, the overall Demak vision is translated into a more specific mission statement for each of the coastal zones identified in Chapter 2. This mission statement takes into account the specific biophysical and socio‐economic opportunities and constraints present.

Coast 0 From Tambakbulusan to Wulan Delta
Given that currently there is no greenbelt and (unproductive or abandoned) aquaculture ponds are present up to the seafront, it is our proposed mission to:

Hold the line, by in the longer term converting aquaculture ponds at the seafront into a mangrove greenbelt for coastal safety as compensated for by revitalizing aquaculture in the hinterland in the short term.

This project will contribute in the following way towards achieving the mission for coast 0:

Greenbelt zone
Sub‐result 2.4: no coastal safety target defined in coast 0, potential to leverage mangrove rehabilitation through Bio‐Rights approach will be explored.

Measures: Feasibility Assessment

Aquaculture zone
Sub‐result 2.5: ~150 ha revitalised aquaculture; of which ~25 ha mixed mangrove‐aquaculture system Measures:

  • Improved water management (150 ha)
  • Introduction of innovative multi‐trophic aquaculture systems (~150 ha)
  • Introduction of mixed mangrove‐aquaculture system (~25 ha)
  • Assisted natural mangrove regeneration/ enrichment planting in mixed mangrove aquaculture system (~ 15 ha)

Coast I/II From Bedono to Surodadi
Given that a greenbelt is lacking and that erosion has taken hundreds of meters of aquaculture ponds, our proposed mission is to:

Advance the line, by restoring the conditions for a mangrove greenbelt and then revitalizing aquaculture in the hinterland to avoid return to aquaculture in the greenbelt zone.

Summarising, this project will contribute in the following way towards achieving the mission for coast I/II:

Greenbelt zone
Sub‐result 2.4: 90 ha mangrove

Measures:

  • Permeable dams to restore sediment balance, spatial arrangement of dams stimulates creek rehabilitation
  • Mud nourishment to restore sediment balance
  • Sand nourishment to restore chenier
  • Assisted natural regeneration
  • Enrichment planting

Aquaculture zone
Sub‐result 2.5: ~150 ha revitalised aquaculture; of which ~25 ha mixed mangrove‐aquaculture system

Measures:

  • Improved water management (150 ha)
  • Introduction of innovative multi‐trophic aquaculture systems (~150 ha)
  • Introduction of mixed mangrove‐aquaculture system (~25 ha)
  • Assisted natural mangrove regeneration/ enrichment planting in mixed mangrove aquaculture system (~ 15 ha)

Coast III Bedono to Semarang
In view of the severity of erosion and subsidence and the peri‐urban nature of Coast III, our proposed mission is:

Managed realignment, by starting a multi‐stakeholder dialogue about re‐alignment of the coastline to a more landward position and about suitable Building with Nature approaches to enhance coastal safety.

For coast III the aim is to initiate a multi‐stakeholder dialogue that will focus on possible strategies for this coastal stretch. Development of a spatial design for coast III is outside the scope of the current project.

Chapter 6 presents a yearly adaptive planning cycle, including yearly updates of the design and engineering plan and associated hardware plan (result 1.6) as based on monitoring and evaluation as well as consultation with stakeholders. This planning allows for alignment with government processes. Further, annual project targets are presented in a Table.

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