T H E S E C O N D W A V E O F D E F E N C E
R E U B E N H O R E - W A T E R H O U S E 3 4 3 6 5 2 4
What can we learn by interrogating the relationship between the destruction zones of March 11, 2011 tsunami to the pre tsunami landscape, and how might this new formed research prepare us for future tsunamis?
Through history we learn from our mistakes, and through past experiences we are able to speculate, understand and potentially anticipate future outcomes. By comparing and analysing the relationship between the past and the present, we are able to inform and advise how we act in the future. However, this process of learning and adapting did not occur in 2011 Japan. Following the tsunami disasters of the past, Japan’s new seawalls were framed as an impenetrable physical defence against future disasters, and this false sense of security is what caused the people of Japan to ignore a history of warnings, such as tsunami warning stones (Facker 2011), and fail to anticipate the consequences of the tsunami wall failing on March 11, 2011 (Onishi 2011).
Through generative mapping of the landscape we are able to interrogate a test site more precisely; information of both the past and present can be extracted, isolated, compared and overlaid, thus enabling the uncovering of realities and representations previously hidden or unimagined (Corner 1999, p. 213). In a 2012 analysis of geospatial data in tsunami flooded areas, for example, Koarai (2012) used generative mapping techniques to compare spacial data, including land use and levels of tsunami damage classification, to ultimately reveal important relationships that can be used to consider reconstruction for tsunami prone areas. This process of historical reflection and adaptation through generative mapping is what this research document aims to interrogate. By comparing the destruction with Japan’s pre-tsunami landscape, I pose the question: What informed the categories of destruction and territory caused by the tsunami of March 11, 2011 on the region of Hashikami, Japan, and why did the tsunami flow in this way? Using mappings as a generative device, this research will identify crucial dependent relationships and morphologies between the pre-tsunami landscape and the destruction zone post March 11, 2011, and will use this knowledge to understand and anticipate the flow patterns of future tsunamis. Ultimately, this study will inform techniques for future mitigation of destruction, rezoning and redevelopment, and will uncover the need to look beyond ‘the myth of absolute protection’ (Rossano 2015, p. 21) toward a framework of resilience for adaption and acceptance (Allan & Bryant 2012). These relationships will be explored at two scales, enabling a deeper understanding of the need for adaptation at both a regional and local level.
In many cases of generative mapping, preliminary mapping studies must first be conducted, where to find ‘x’ you must first explore ‘y’. The first of these mappings explores land use data and the existing spacial conditions of Hashikami, acting as a control map for new relationships to be built on and compared. By considering topography and population distribution, the control map informed common settlement patterns, and identified materials in the form of generalising program, including farm zones, the topographical features and slope of the landscape, and the thick vegetation and hard surfaced coastal regions and roads that existed pre-tsunami.
RICE FIELDS RICE FIELDS CONFIG.
THICK VEGETATION
INDUSTRIAL / COMERCIAL
CONCRETE
RESIDENTIAL ROADS
RICE FIELD DECLINE DIRECTION
TOPOGRAPHY 1M INT.
BUILDING STRUCTURES
OUTLET
PRE-EXISTING MORPHOLOGY
The second of the mappings built upon the control map, classifying and aligning the territory of destruction zones. This map was constructed similarly to Hasegawa and colleagues’ (2012) geographical analysis of flooded areas caused by the Great East Japan Earthquake, using mobile mapping to categorise destructive territory by severity through arial photograph (1 being most destructive, 3 being least destructive; Hasegawa et al 2012). The identification of these destructive territories then became to protagonist by which to understand and identify relationships, through comparison of the mappings, between the existing pretsunami and post-tsunami conditions, thus resulting in clear categorisation and boundaries.
DESTRUCTION ZONES
DESTRUCTION Z 1
DESTRUCTION Z 2
DESTRUCTION Z 3
SAFE ZONE
DESTROYED STRUCTURES
STANDING STRUCTURES
DESTUCTION ZONES v LANDFORMS
UPFLOW DIRECTION
1
4
DESTRUCTION ZONES v PRE-EXISTING MORPHOLOGY
3
2
Using mappings similar to Patanakanog and colleagues (2007), a generalised up flow was then produced to provide more insight into the direction of the flow of the tsunami in relation to the existing morphology (Patanakanog et al 2007). Through this directional mapping it was found that where coast regions were predominantly flat the tsunami moved in random directions, resulting in less resistance and hence faster speeds, whereas in areas with mountainous terrain the flow was manipulated and redirected in various ways. It was not until the combination of these maps, which revealed overlapping lines, clashing territories and untouched zones, that the relationship between the two mapping states became abundantly clear, thus apprising the main point of interrogation in this research. However, this information was not enough generatively to imply understanding or inform future research at its current scale. It was through the act of extracting that enabled a much more intricate examination of how certain morphologies, such as rice field configuration (Figure 1), thick vegetation (Figure 2), steep topography (Figure 3) and inlets (Figure 4) directly impacted tsunami flow. This extraction was examined closely with the destruction, speed and direction data curated in the preliminary mappings, enabling the illustration of the scale of this new-found relationship. Even so, this new map failed to convey information on time, duration and volume, instead representing the relationship two-dimensionally without hierarchy and making it difficult to understand the layers and how they relate and inform one another.
FIG 1.
FIG 2.
FIG 3.
FIG 4.
This issue of two-dimensionality was addressed using the production of axonometric drawings, allowing the clear illustration of specific relationships and behaviours in each extraction. The axonometric provided the exploration of relationships with heights and volumes, and expanded on the duration of destruction versus visual height of the morphology. Analysis of this research revealed characteristics or patterns (that were annotated as the tsunami’s reaction) that the morphology had on the flow of the tsunami, including flow characterised by the act of splitting, absorbing, retaining material, slowing, dissipating and redirecting.
9 10
6
9 8 5 7
Figure 5 explores one of the post-tsunami safe zones, interrogating why the area was left untouched by destruction despite its flat gradient and position in the high destruction zone. Exploration revealed the importance of the thick vegetation in the area, which forced the tsunami to split, potentially slowing the force and speed of the flow. Although the safe zone was potentially inundated, the extent of the damage was not recorded as severe and this thus suggests that vegetation may play a role in slowing the force of a tsunami and therefore mitigating its damage.
SPLIT FIG 5.
Figure 6 explores the flow of the tsunami in regard to rice terraces through mapping. Here, the destructive force of the tsunami was absorbed by each terrace as the tsunami inundation line rose, illustrated by movement lines in the landscape. This ability of the rice terraces to somewhat minimise the destruction of the tsunami furthermore highlights a potential structural design that could be integrated into specific territories, allowing for more informal mitigation techniques.
ABSORB FIG 6.
MATERIAL RETENTION FIG 7.
Figure 7 shows the relationship between hard and soft materials that defined the destructive zone. Hardsurfaced materials retained their form, and areas predominantly consisting of these hard materials were thus mistakenly mapped as ‘safe zones’. Conversely, soft materials were predominantly washed away causing more damage due to geological performance with tsunami flow. These differences in the performance of zones with contrasting materiality indicate the need for further study of the geological territory of existing topographies, in order to understand which areas are more susceptible to soil deprivation.
SLOW FIG 8.
Figure 8 demonstrates the relationship between the topographic fold of the inlet and the direction and flow of the tsunami. It was revealed that the dip, although not completely stopping the tsunami flow, caused it slow and slightly redirect with the decline towards the bay, mitigating destruction in adjacent areas. This fold was the primary topographical feature that informed the destruction territory of zone one and zone two.
DISSIPATE FIG 9.
Figure 9 explores the relationship between the existing topography and the tsunami inundation heights. It demonstrates the morphology’s ability to dissipate the tsunami flow in relation to various heights and the topography’s ability to ‘accept’ tsunami flow, thus creating various destruction territories given these heights. By exploring the relationship between different topographies and the tsunami height inundation line, we can start to suggest ways in which tsunami heights can be allowed into the landscape as a means of mitigating destruction on other parts, and through the understanding of these relationships generalised territories such as mappings can be explored in other topographic studies.
Figure 10 examines the existing topography off the coast. Although providing safety in higher ground, when mapped with the destruction zone analysis revealed that something caused the tsunami to redirect; the force of the water was severely altered due to the steep coastal topography as it moved downwards. This change in flow strength may have been the cause of high destruction in adjacent lower-lying areas. Although mapping direction, this depiction fails to represent the force and speed of the tsunami, which may help to articulate the destructive power of the flow as it is redirected. Its this research that might aid in the recognition of redirection threats in the region, which can then be used to identify hazard zones for future development. This act of identifying redirection may also be seen as a strategy for designing, where redirecting the water in particular ways could be used as a way of mitigating the destructive power to other areas.
REDIRECT FIG 10.
Although the exploded axonometric was highly generative in understanding the relationship between two factors, it focused solely on exploring the individual facets of potential mitigation (i.e. topography, material, structure) and not on the ramifications of their combination. That is, it did not take into account the multiple dependent relationships that might have made the tsunami react in a particular way. In Patanakanog and colleagues (2007) study, revealing the relationship of landforms on tsunami flow, a strong correlation was uncovered between destruction boundaries and existing morphology, resulting in site-specific reactions of flow (Patanakanog et al 2007). It was through this similar understanding of natural disaster relationships that Rossano (2015), in her study on flood management, recognised the role of farmland and the relationship between water volume and existing topography. In the case of extreme flooding, the farmland became the mitigator for absorbing large amounts of water, preventing wide spread destruction downstream through this process of designing with resilience in mind. Though not suggesting specific design implementation, this research has revealed strategies for understanding the landscape as a series of interwoven relationships, and explores how these relationships can inform new ways to respond to tsunami flow, develop new territories and mitigate future destruction. It articulates a discourse around how we can use these, and other undiscovered, strategies for the future, and identifies the need to continue to employ a framework of resilience for designing the landscape for tsunamis. And, as these relationships continue to re-appear in the region, further generative mappings can be produced.
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