background | time horizon | shoreline protection | vegetation succession | site assessment |designed prototypes

Background information

The coastal margins of the islands of Indonesia are some of the most populated areas in the world. Most of the people living in Aceh Province live along a coastal ribbon within 5 kilometers of the ocean. It is said that significant damage inland from the coast for only about 1 -2 km for most of the coastline, but up to 3 -5 km in low areas and around the provincial capitol of Banda Aceh, which is located in a low lying area.

Areas most significantly affected were in the heavily populated cities. The tsunami inundation and damage was not uniform. The geographic orientation of impact reflects the geomorphology of the land mass as well as the bathymetry beneath the water close to the shoreline. Some areas were hard hit such as Lho-nga, which was completely swamped by water. It appears a large mass of water pushed over the land by force and did not recede. Cities and heavily populated areas also happened to be in target areas of high impact. Unlike other types of disasters, such as hurricanes, the area impacted by the tsunami was not large when compared to the total area of the province. The total area extent of impact was 413 km 2, which is a small percent of the total provincial area. However, because of the high population densities in this narrow coastal zone the human impact was nonetheless extremely large.

It is important to note that while this tsunami was unusually large, and that its magnitude contributed significantly to its heavy toll, it is also true that other factors contributed to the great loss of life. As development of the coastal margins has grown, its vulnerability has also increased. Human impacts to shoreline areas, such as over population, deforestation, and over fishing, exacerbates the damage caused by tsunami. A healthier shoreline is badly called for future relief and development. Since people will eventually come back where they were, it is necessary to have a clear vision about the shoreline rehabilitation. This workshop mainly deals with the steps for reestablishing and reconstructing the shoreline areas and its vital ecosystem in the manner of naturally friendly and sustainable. Various methods for shoreline reinforcement are suggested;three prototypes based on the current situation of Banda Aceh are generated for further remediation. The overall concept is to integrate the artificial as well as the natural methods to rehab a healthy shoreline ecosystem, and pay special attention to the spatial relationship between the human settlements and shoreline natural system.

Time Horizon

0-1 yrs....

+Reinforce and reconstruct damaged shoreline using both artificial methods and natural friendly methods -
After tsunami, shoreline area was badly eroded with great lost of surface sand and soil. Worse still, the land was no longer capable to retain sand and soil against constantly tapping sea water. Before large scale reforestation being implemented, it is important to prevent shoreline area from further erosion and make it strong enough to accommodate vegetation in this time period.
+Clear up debris and prepare land for revegetation -
Massive debris generated by tsunami could be made use of to build up protection structures
+Integrate the rehabilitation sites with the new settlement for manpower efficiency -
Newly developed shoreline need to be taken care of. Local people settled in near shore area can participate in the shoreline rehabilitation process. It is also possible to form some memorial ritual such each family help to take care of one segment of the revetment site and have their death’s name on the stone to be memorized.

+Large-scale reforestation in shoreline area according to different types of coastal ecosystem -
Coastal ecosystems provide shoreline stabilization and buffering services. Some concerns about the shoreline revegetation are the access to the sea. The scale of the shoreline forest and its relationship with the inland settlement should be well handled to ensure the efficiency of the natural system without forcing local people to change their way of marine life too much. Access can be made together with the estuaries of the rivers.
+Set up non-developed barren land for eco-recover -
Since people are wiling to move back to their original land near shore, some restrains should be made in the early years of eco-recover to ensure that there is no more disturbance on the ecosystem. non-developed areas serve as the transition and buffer from the human settlement to natural system.

5-10 yrs....

+Nurish and aggradize vegetation coverage
+Gradually resettle to non-developed areas-
The final stage of rehabilitation is to join the human settlement with the natual system. The non-developed areas in the second stage would be developed to co-existence areas for people and the nature.

Shoreline protection

After tsunami, vast shoreline areas were totally damaged left the badly eroded bare land. The first and foremost task for the local community to reestablish shoreline areas is to reinforce the coast both resort to artificial methods and natural friendly methods.

Abstract

• Artificial methods

seawall	grion	artificial dune
jetty	gabion mat	detached breakwater

• Natural friendly methods

Beach nurishment	mild slop revetment	sand fence
beach grass	mangrove forest	mangrove and fish pond

Vegetation Succession

The main ecosystem modulators are temperature, salinity, chemical suitability and physical sustainability. Coastal ecosystem in Sumatra can fall in to the category of mangrove forests, beach vegetation, brackishwater forests rocky shores and coral reefs. Based on the shoreline topography and local climate, two types of vegetation succession are listed below. Each type can fit into types of the context of the spatial sequence discussed above.

Coastal Dune

Vegetated dunes can occur on sandy seacoasts to support plant growth and sufficient wind action to move sand. Coastal dunes, particularly those of the barrier type, have a value well beyond that of habitat, serving as coastal protection and preservation in several ways. Continuous barrier dunes serve as flexible barriers to storm surges and waves and are of particular value in affording protection to low-lying backshore areas and in helping to preserve the integrity of low barrier islands. Dunes provide protection more effectively and at a lower cost than a seawall. The dune complex divideds into three zones: the pioneer zones, the intermdiate or scrub zone, and the back dune or forest zone.

Mangrove Forest

source: ‘Daintree Mangroves” - January 2004, the university of Queensland

Site assessment

This workshop mainly focuses on the badly damaged shorline areas in Banda Aceh The main indicator are climate zone, vegetation distribution and shoreline topography. Banda Aceh is in the dry climate zone, with relatively flat beach. The topography and the relationship between shoreline area and inland settlement determine the coastal rehabilitation type, while vegetation distribution determines different types of vegetation succession.

• Different types of climate zone in Sumatra
• Different types of vegetation zone in Sumatra

• wide sloping shore with further inland eroded area
• this type is from highly damaged area in Banda Aceh, where 3.3km extensive debris is further inland. Situation now is severe with barrier lands suffering from further erosion.

• immediate shore with adjacent massive debris
• this type is from the northern most part of Banda Aceh, where the shoreline and settlement were totally damaged. The damage is so sever that the shore configuration has been changed a lot with intensive inundation area and receding foreshore.

• damaged shoreline with adjecent aquaculture area
• this type of shoreline habitat is widespread all over Banda Aceh. The former aquaculture ponds were inundated or destroyed, left the newly forming lagoon or contaminated lakes.

Designed prototypes