The Efficacy of Coastal Road Development to Protect West Coast of Jepara from Abrasion and Future Sea Level Rise

This study examines the discourse of developing a coastal road as a solution to protect the western coast of Jepara in the long term from the threat of coastal hazards and climate change. Therefore, attempts to understand the coastal conditions of Jepara in the past, present and future are critical. This study shows the abrasion in the region is inseparable from the history of this area which was formed by the material deposition of Mount Muria. At present, the coastal conditions particularly in Kedung and Tahunan Districts are very prone to abrasion. A result of the Digital Shoreline Analysis System over the last two decades (2001-2020) showed a shift on Kedung District’s coastline ranging from 78-701 meters landward, while it was about 1.4-36.8 meters landward and 10.3-34.5 meters to the seaward in Tahunan District. Analysis of land cover and land use show that most of the loss of land due to abrasion were ponds, rice fields, and settlements. Sea level rise will exacerbate this condition. With the projection of global sea level rise which increase by 21 cm in 2060 and by 53 cm in 2100, ponds, irrigated rice fields and settlements in this region will be submerged with an economic loss of IDR 2.97-3.06 trillion or nearly to USD 205 million. Our study concludes that the construction of coastal road will not provide much of the expected protection function, unless the development of supporting infrastructure, especially polders, and several other supporting options, are developed in an integrated manner.


Introduction
Despite its potential, coastal areas are threatened by disasters such as abrasion, tidal floods, and subsidence due to sea level rise (SLR).These disasters are also experienced by the coastal areas in the Jepara Regency, which has almost 83 km of coastline.Kedung and Tahunan Districts which are located on the west coast are the most affected, particularly from abrasion and it significantly affect coastal communities [1,2].A number of efforts have been made by the local government as a part of mitigation, such as trough planting vegetation, constructing breakwaters with bamboo, and building embankments.Yet, these are not optimal and need to be improved due to various factors, especially the limited financial capacity.Recently, the central government has raised a discourse on constructing a coastal road, a road built parallel to and directly adjacent to the coastline, to overcome abrasion and coastal problems in Jepara, while it is also useful to increase regional mobility.1264 (2023) 012017 IOP Publishing doi:10.1088/1755-1315/1264/1/012017 2 An infrastructure-based approach for disaster mitigation provides both advantages and disadvantages.Infrastructural development could solve problem and deliver solutions quickly.As a popular policy, this approach often receives a community support that would benefit from its existence.However, this kind of approach generally requires substantial funding beyond the capacity of local government.A large-scale infrastructure project in a particular area is usually inseparable from the role of the central government, especially in terms of funding.Meanwhile, scientists and environmentalists generally criticize this approach for long-term effectiveness [3,4].Recently, more and more scientists consider the development of blue and green infrastructure to address flooding and coastal abrasion.Despite its potential and rising popularity [5], this concept also has limitations, especially in dealing with problems with a severe scale of magnitude, and when the fast results are required.
Both the conventional and green infrastructure development are generally oriented towards protection against the issue of flood and abrasion in the coastal area.Other strategies, such as accommodation, relocation, and advance, are alternatives that should be considered [6][7][8].This study discusses the idea of coastal road development and place it within the discourses of making sustainable response choices for the future.Therefore, attempts to understand the coastal conditions of Jepara in the past, present, and future are critical.Specifically, this study explores the impact of abrasion that has been occurred in the last two decades and the effect of sea level rise on the west coast of Jepara.This study also discusses the response of the local government that has been carried out to deal with this problem and the efficacy of the coastal road development in creating sustainable solutions in the future.

Data and Methods
The study area focused on the west coast of Jepara, with particular emphasis on Kedung and Tahunan Districts, which cover area about 9076 hectares and has a total population of approximately 187 thousand.This study used secondary data from BPS, Geoportal Jawa Tengah, USGS, Google Earth, and Ina Geoportal for spatial analysis.We employed GIS in this study to identify the location and distribution of infrastructure, abrasion patterns, sea level rise, and their relation to the distribution of land cover and land use.Meanwhile, primary data was obtained through field observations and interviews with key persons.The selection of key persons was focused on those locals who have lived in the study locations for long period of time and communities related to coastal life, such as fishermen, salt farmers, or those with authority in managing coastal issues.Therefore, apart from interview with local community, interviews were conducted with government officials at district and sub-district levels and other key persons at the disaster management board, local development and planning agency, public work and housing agency, and environmental agency.The focus of the interview includes the history of the development of the Jepara coastal area, socio-cultural conditions, and people's lives, as well as the experiences and aspirations of the people toward responses to abrasion and their attitudes on coastal road development plan.Primary data confirms the spatial analysis results and explains the patterns and phenomena in detail.Figure 1 below provides a summary on the data and methods of the study.

Historical and Existing Contexts
During the interglacial period, the area around Mount Muria, consisting of Jepara, Kudus, and Pati, was separated from Java by the Muria Strait.In the pre-colonial period, under the Demak Sultanate, Jepara Regency was a well-known maritime city with most people working in the trade and cruise ship sectors.The glory of the Jepara region then started to fade since 17th century following the eruption of Mount Muria leading to the silting and sedimentation of the Muria Strait and rivers.Mudflows and avalanches from the eruption gave rise to a new land, including what is currently as Kedung and Tahunan Districts [9].So, these districts are prone to abrasion based on its historic geographical factors and the characteristics of the muddy land formation, which has no coral protection.
Currently, around 187 thousand people inhabit the west coast of Jepara Regency.Approximately 58% are in Tahunan District and 42% in Kedung District.However, population growth in Kedung (0.82%) was slightly higher than the average (0.68%) during the period of 2010-2020 [10].Of the nine villages on the coast of Kedung and Tahunan, most of the population lives in Kedung District, with concentrations in the villages of Kedungmalang (23%), Surodadi (19%), and Tegalsambi (16%).
Most of people in Kedung District work in the primary sector, such as fishermen, aquaculture, and paddy farmers.Kedung District has a Fish Auction Facility (TPI) located in Kedungmalang Village.However, salt mine activities have an enormous economic contribution to the district, approximately at IDR 13 billion annually.Meanwhile, the residents of Tahunan District, apart from relying on the agricultural sector, also work in the handicraft industry sector, especially furniture and carvings, as well as the tourism sector.Industrial activities, especially furniture and carving, contribute an economic value of IDR 200 billion annually.
The level of welfare in Tahunan District has improved.The number of households under the poverty line decreased significantly from 5,427 to 2,174 in 2010.Meanwhile, the improvement in people's welfare in Kedung District was insignificant.Families below poverty line only fell 12% during the same period leaving around 6,108 household remains in poverty in 2010.
The land use of Kedung and Tahunan District in 2017 was dominated by ponds covering about 1151.4 hectares, followed by rice fields (594.9 hectares) and settlements (261.9 hectares).Mangrove land use is only about 2.3 hectares.The results of map processing from ESRI Land Cover (Figure 2) show an increasing of land cover area in the wetland of almost 76 hectares, flooded vegetation of 5.2 hectares, a built area of 375 hectares, a bare ground of 0.04 hectares, and range of 27.8 hectares.The decreased land cover area is identified as trees approximately at 68.Using satellite imagery and applying the USGS Digital Shoreline Analysis System, shoreline changes in 2001, 2010, and 2020 can be presented in Figure 3.The analysis results show that Kedung District shoreline has experienced a declining due to abrasion, almost at 267 hectares with a shoreline retreat of 78-701 meters inland.Meanwhile, the coastline of Tahunan District has experienced a declining of land approximately at 6.08 hectares with the shift of the coastline towards land or abrasion at 1.46-36.8meters, and seaward or accretion at 10.3-34 meters.
Abrasion in Tahunan District is more controlled than Kedung due to the presence of mangrove, especially on Teluk Awur water area.Even several areas experienced accretion due to protective structures such as groins and small piers that function as sedimentation trap.The presence of coral reefs in the district also helps to reduce wave energy.Aquaculture is the most affected type of land use and is prone for being affected by abrasion because it is in direct contact with the sea.
This region continues to experience physical development.There was an increase in the number of facilities such as education, health, worship, trade and services, and recreation from 2009-2022.These facilities are generally in good condition, with elevated construction to anticipate tidal floods.The drainage conditions are relatively good and equipped with water gate facilities on river sections to regulate the rate of water flow.Electricity, drainage, and road networks have also increased over this period.The electricity network in this area has served household demand with the average of 900 Watts.The telecommunication network is also available in all villages.Community mobility in this area has been supported by a road network that has been paved, although some sections are still damaged.Clean water remains an issue, primarily related to the network that has not yet to reach this area.Meanwhile, the supply of clean water in this area is limited due to seawater intrusion.Solid waste is another problem due to limited temporary disposal facilities, low service levels, and low public awareness.Table 1 summarizes the potentials and problems on the western coast of Jepara, which could add to the complexity of response in dealing with the issue.• The water of Tahunan District is protected by piers and coral reefs and are used for tourism and micro-business activities.
• Small jetty facilities and fish auctions are available to support fishing activities.The majority of people in Kedung work in this primary sector.
• The furniture and carving industry have penetrated the world market every year.
• A local community association for tourism has been established.
• Abrasion occurs predominantly in Kedung District.The majority of this prone area has not equipped with wave breaker facilities and lack of coral reef • The alluvial soil in Kedung District is not really suitable for mangrove to grow.Lack of effort to mangrove conservation and cultivation.
• Ponds are very prone to abrasion, and there are still settlements around riverbanks and beaches which are prone to disasters.
• Most of the rivers have no dyke and disaster evacuation routes are not yet available.
• Fishermen's activities in the mangrove sedimented area exacerbate coastal abrasion.

Current Response and Future Discourse
Generally, infrastructure development remains one of the most preferred solutions for solving abrasion and flooding problems in coastal areas.Despite its controversy, large-scale infrastructure development promises instant results.For example, in the northern coast of the border between Semarang City and Demak Regency, the neighboring districts of the study area, the construction of almost 27 kilometers sea toll road is underway connecting Semarang and Demak.It is seen as one of the efforts to deal with tidal flooding, especially in the Kaligawe and Sayung Districts, as well as providing a solution for traffic jams.The construction of the toll road is complemented by the construction of polders.Public Private Partnership (PPP) scheme is selected by the Toll Road Business Entity (BUJT) with a budget of IDR 4.3 trillion to financing the project [11].
Then, discourse on constructing a coastal road on the west coast of Jepara was rolled out to address the problems of abrasion, flooding, and future SLR.Technically, about 21 kilometers long coastal road will be built in an integrated manner with the sea wall and connected to Jepara, Mlonggo, and Bangsri.Apart from protecting the coastline, the coastal road is also expected to create economic growth in the surrounding area.An estimation shows that this development will require a budget of IDR 318.6 billion and will be divided into four road segments, namely: (1) Kartini Beach to Jepara Outer Parkland, (2) to Blebak Beach, (3) to Bondo Beach, and (4) to Tanjung Jati Power Plant.

Abrasion and SLR in the Future
The IPCC AR 6 report shows that the global average sea level rise during 1901-1990 was 1.35 mm and then accelerated to 3.25 mm per year from 1993-2018 [12,13].IPCC AR6 2022 with a moderate scenario SSP2-2.4.5 also projects that sea level rise will continue, and in 2100 it will increase by 0.44-0.76meter calculated from the baseline in 1900 [14].
Meanwhile, Indonesia's sea level rise anomaly in the 1993-2015 was recorded at 210-240 mm, with an average increase of 3 mm per year.World Bank [15] also states that global sea level rise ranged from 0.36 -0.71 meter in the 1986 -2005 with an increase of 3.5 -8.8 mm per year, so it is estimated that up to 2100, there will be an increase of 0.53 meter with an average of 6.1 mm per year.Figure 4 presents the analysis results of the areas affected by the SLR in 2060 and 2100 in the study area.About 0.21 meter of SLR in 2060 will submerge the coastal areas in Kedung and Tahunan Districts, covering about 1002.5 hectares.An overlay between SLR projection data on 2060 and the existing land use shows the IOP Publishing doi:10.1088/1755-1315/1264/1/0120176 impact of inundation to 710.9 hectares of aquaculture, 10 hectares of residential, and 16 hectares of irrigated rice fields.
In 2100, the increasing of 53 cm a sea level rise will inundate 1123.8 hectares of coastal areas in the regions.It is about 10 percent increasedapproximately at 121.3 hectaresin comparison to inundation in 2060.In 2100, about 795.1 hectares of aquaculture pond will be lost, 11.4 hectares of the residential area will be submerged, and 31.1 hectares of irrigated rice fields will be failed.
Without any interventions, SLR will submerge five touristic areas, four educational facilities, two trading facilities, and a temporary disposal site in Teluk Awur Village.Analysis of abrasion and the impact of SLR on land use productivity shows that there will be economic losses in the two districts approximately at IDR 631 billion until 2060, assuming the average profit of salt mines is about IDR 11.4 million/ hectare, the average price of fishery products is IDR 36,000/ kilogram, the average yield of food crops (paddy fields) is IDR 8.1 million/hectare, and the average price for a 150 square meters house is about IDR 350 million per unit.Assuming the same calculation, then, the estimation of economic losses in 2100 due to abrasion and SLR will reach at IDR 717 billion.
Based on the average land value of around IDR 3 billion/hectare, it is estimated that the loss of land affected by abrasion and SLR in 2060 is about IDR 2.34 trillion, and in 2100 it became IDR 2.69 trillion.The tourism sector as an emerging prime mover will experience an economic loss of around IDR 390.7 million per year.Overall, considering land use productivity, land ownership, and tourism, the total economic loss is estimated at IDR 2.97 trillion in 2060 and IDR 3.06 trillion in 2100.

Options and Analysis Framework
There are a number of options to address abrasion and SLR, from hard to soft structural-based solutions, and from engineering to social solutions.However, all of this must be appropriate and relevant to the characteristics and context of the potential and problems in a particular area [16].Basically, these options can also be grouped into several categories based on interaction strategies between land and oceans, namely: (1) protection, (2) adaptation, (3) relocation, and (4) advanced [6].Furthermore, these strategies can be applied to five urban and regional life sectors: production, settlements, infrastructure, conservation, and community space.
When all these perspectives are integrated, an analytical framework can be used to diagnose trends and prospects for future solutions, as presented in Table 2.The table shows several important points.First, constructing a coastal road is only one of the many options that can be implemented when IOP Publishing doi:10.1088/1755-1315/1264/1/0120177 financing does not become a constraint.Second, developing a coastal road should not allow other options to be ignored but integrated.
To determine the best option to be implemented, the advantages and disadvantages of each option need to be identified, and a simple scoring can be applied.In this context, constructing a coastal road has several advantages and disadvantages.These advantages include: (1) the ability to productive land in the form of salt mines which are directly adjacent to the ocean, (2) the ability to protect vulnerable residential areas around the coast, (3) allow people to access marine resources and maintain their economic resources and (4) strengthening regional mobility.Meanwhile, the weaknesses include: (1) expensive financing, (2) may attract economic investment and speculation which then increase the vulnerability of areas with the intensification of densities, (3) the location of coastal road development is not yet definitive and not necessarily in a location that can protect the areas subject to abrasion.

Future Direction
Given the multifaceted and interrelated characteristics of the problems, constructing a coastal road alone will not be able to solve the abrasion, rising sea level and the occurring impacts.This result confirms previous study [3,4] indicating the limit of infrastructure-based adaptation, especially for a long-term solution.For example, a coastal road will not be able to resolve fluvial flooding and erosion caused by overflowing rivers before they enter the sea.Hence, elevating the river embankment needs to be considered.As another example, a coastal road will not be able to reduce wave strength, so it needs to be combined with a breakwater.Briefly, in the short term, a protective approach can be implemented and need to be combined with other protective solutions.Therefore, the integration of blue and green infrastructure [5] to address flooding and coastal abrasion should be prioritized.In the long term, a more sustainable solution, including solutions oriented towards relocation and advance onto the water [6][7][8] need to be considered.
In the context of addressing the impacts of abrasion and SLR in the future, the discourse on developing a coastal road on the west coast of Jepara Regency is not enough without being integrated with sea walls, river dyke, and retention ponds into an integrated polder system.The application of this system later must be supported by several policies, such as land consolidation to arrange prone settlements around the riverbanks and coastlines.This effort also serves as a tool to provide green open spaces that function as natural protection and conservation zones.Developing floating houses and settlements can be an alternative for people unwilling to relocate.As a coastal area with the majority of the population making a living as fishermen, it is also necessary to consider increasing the function and capacity of the dockside, equipped with breakwater infrastructure to protect the coastline.

Conclusion
Abrasion and increased SLR are the main threats to coastal areas in the west coast of Jepara Regency.The government has made various countermeasures, such as building embankments, even though they are not optimal.This study identified various options in dealing with abrasion and SLR, including the emerging idea of developing a coastal road.It concludes that coastal road development cannot solve the current abrasion and future issues of SLR without being combined with other shortterm protection approaches.The other options which have longer term orientation, such as through adaptation, relocation, and advancement, need to be further explored in the context of the west coast of Jepara.A high complexity and multi-dimensional problem require a variety of appropriate solutions.Limiting options by putting forward only short-term options closes the opportunity to gain a sustainable outcome in the future.Follow-up studies to find out the advantages and disadvantages of each option can assist decision makers in choosing a comprehensive set of policy options for addressing coastal issues sustainably.

Figure 1 .
Figure 1.A Summary on the Data and Methods of the Study 2 hectares and crops of 418.1 hectares.(a) 2017 Land Cover Map (b) 2022 Land Cover Map

3 .
(a) Kedung District Coastline Changes (b) Tahunan District Coastline Changes Figure Map of Changes in the West Coast Coastline of Jepara Regency (Author, 2023) (a) 2060 and 2100 Abrasion Affected Area Map (b) 2100 Abrasion Affected Land Use Map

Figure 4 .
Figure 4. SLR Impact Areas on the West Coast of Jepara in 2060 and 2100 (Authors, 2023)

Table 1 .
Some Potentials and Problems in Kedung and Tahunan Districts

Table 2 .
Possible Options for Dealing with Abrasion and SLR in Western Coast of Jepara