experiences and diffusion of information on

UNIVER SIDAD
DE
CONCEPCIÓN
DEPARTAMENTO DE CIENCIAS DE LA TIERRA
10° CONGRESO GEOLÓGICO CHILENO 2003
EXPERIENCES AND DIFFUSION OF INFORMATION ON
ENVIRONMENTAL GEOLOGY FOR LAND USE PLANNING IN SOUTH
CENTRAL CHILE
MUÑOZ, J. 1, ARENAS, M.1, BEHLAU, J.2, HANISCH, J.2, HELMS, F. 2, JARA, C.1,
MILOVIC, J.1, PÉREZ, Y.1, RENNER, S.2, TRONCOSO, R.1
1
Servicio Nacional de Geología y Minería, Oficina Técnica Puerto Varas, La Paz 406, Puerto Varas, Chile,
[email protected]
2
Bundesanstalt für Geowissenschaften und Roshstoffe, Stilleweg 2, D-30655, Hannover, Germany
ABSTRACT
Integrated studies on environmental geology for land use planning have been completed in the Puerto Montt, Osorno
and Valdivia areas in south central Chile, including present day land use, geology, geological hazards, groundwater,
hydrochemistry, industrial rocks and minerals and, in cases, seismic response and foundation soils thematic maps.
These experiences have permitted to identify and study relevant environmental geologic topics for each particular
area and to define main communications and diffusion problems and necessities. Although currently increasing, the
generated information is weakly understand and applied by local authorities and communities. During future
environmental geologic studies in south central Chile, organised diffusion and education programmes oriented to
local authorities and communities must be developed and applied before, during and after the completion of the
study in a specific area. Future development of environmental geology needs to consolidate expertise in new and
emergent topics and improve the generation of quantitative data.
INTRODUCTION
Integrated geologic environmental studies oriented to land use planning and environmental
management on regional scale have been already completed for the Puerto Montt, Osorno and
Valdivia areas in south central Chile (Figure 1). A similar study is currently in progress in the
Temuco area and other is planned for the Castro region in the main Chiloé Island. These studies
include the collection of information and preparation of digital thematic maps about geology,
geological hazards, groundwater resources, aquifers vulnerability and industrial rocks and
minerals, among others. The relevant information taken from each of these thematic maps is
integrated in a synthesis map of recommendations. Both thematic and synthesis maps have been
produced using geographical information systems and data bases. The main goal of these maps is
to compile and make available geologic environmental information to support local and regional
land use planning.
The completion of environmental geologic studies requires active participation of both private
and public organisations and local communities in order to exchange experiences and
information. Also, each particular area needs to be considered as unique, identifying its priorities
Todas las contribuciones fueron proporcionados directamente por los autores y su contenido es de su exclusiva responsabilidad.
synthesis map should be written end
explained in a simple way to allow a better
understanding and application of potential
users.
STUDIED THEMES
The following topics have been compiled
and integrated in thematic maps and
summarised in the synthesis map (Figure
2):
Vulnerability and contamination hazards.
The map displays information about
vulnerability of groundwater resources
according to economic activities such as
industries, agriculture, building material
exploitation and location of waste disposal.
Together
with
the
hydrogeological
information allows to identify eventual
contamination hazards to water resources
and to recommend mitigation actions.
Figure 1. Location of completed, currently in
progress and planned environmental
geologic studies for land use planning in
south central Chile.
Geological hazards and geothecnical
problems. Including zoning of areas expose
to landslides, erosion and floods. Land use
planners must take these areas as hazard
zones and apply prevention and mitigation
programmes.
and relative importance of each theme. The
information presented in each thematic and
Hydrogeology and hydrochemistry. This thematic map classifies the groundwater resources
according to available amount, potential, quality and accessibility for an eventual future use.
Planners should strongly take in account this information to ensure future requirements of water.
Volcanic hazards: The map limits zones exposed to lava and pyroclastic flows and ash fall
deposits. The planners should take these zones as restricted for land use and ensure prevention
and/or mitigation actions.
Industrial rocks and minerals. Indicating zones and characteristics of building materials, such
gravel, sand, clay and ornamental rocks. The most important zones showing no conflict with
other resources (i.e., water resources), are recommended and should be reserved for extraction
materials.
Todas las contribuciones fueron proporcionados directamente por los autores y su contenido es de su exclusiva responsabilidad.
SHYNTESIS MAP
Recommendation for extraction
Superficial and groundwater
Industrial rocks and minerals
Recommendation for protection
Superficial and groundwater
Nature
Geological site
Civil infrastructure
General recommendations
Waste disposal sites
Groundwater monitoring
Hazard mitigation/prevention
Floods
Landslides
Soil foundation
THEMATIC MAPS
Present
land use
Geology
Geological
hazards
Industrial rock
and minerals
650 km .
650 k m.
650 k m .
66 0
67 0
66 0
67 0
680
660
670
Hydrogeology
69 0 k m.
680
69 0 k m .
690 k m.
68 0
650 k m .
66 0
67 0
690 k m.
68 0
55 40 km .
55 4 0 k m .
5540 k m.
55 40 km .
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554 0 km .
554 0 k m .
554 0 k m .
553 0
55 30
55 30
55 3 0
553 0
553 0
553 0
553 0
552 0
552 0
55 20
552 0
55 2 0
55 20
552 0
552 0
55 10
55 10
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55 10
55 10
55 10
551 0
551 0
55 00
55 00
55 00
550 0
550 0
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55 0 0
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549 0 km .
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54 90 k m.
54 9 0 k m .
54 9 0 k m .
549 0 km .
650 km .
54 90 km .
66 0
670
680 km .
54 90 km .
65 0 km .
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660
67 0
680 k m.
660
67 0
680 km .
65 0 km .
660
67 0
680 k m.
Figure 2. Sketch of results included in main thematic maps and integrated synthesis map for
the Osorno area.
Synthesis of recommendations. This map integrates the most relevant information of each
thematic map. The recommendations include protection of groundwater resources, zones exposed
Todas las contribuciones fueron proporcionados directamente por los autores y su contenido es de su exclusiva responsabilidad.
to geological hazards, zones recommended for extraction of building materials and for waste
disposal. The recommendation outlines in this map need to be considered as general guide for
planning purpose. However, for specific topic authorities should use the respective thematic map.
Not enough expertise has been achieved yet in some relevant thematic such as soil foundation,
seismic response, applied geophysics and numeric information. For these reason, no thematic
maps on some of these topics have been prepared for all studied areas. This is in part due to lack
of specialists and necessary equipment.
STUDIED AREAS
PUERTO MONTT
The most important geological topics in the Puerto Montt area are geological hazards,
groundwater resources and exploitation of sand and gravel. The geological units include
Quaternary glacial and glaciofluvial deposits mainly related to last glacial cycle and volcanic
deposits associated to Calbuco and Osorno volcanoes. Geological hazards are represented by
landslides along the coast of Puerto Montt (SERNAGEOMIN, 1998, Antinao et al., 2000),
mainly triggered by hydrometeorological conditions. The eventual eruption of the explosive
Calbuco or Osorno volcanoes is a high priority volcanic hazard in the area (Moreno, 1999 a y b;
Petit-Breuilh, 1999). Locally, the erosion of bridge foundations and drain obstruction leading to
road collapse are also present in the area.
The main high quality aquifers are located within highly permeable glaciofluvial deposits. In
some localities, a high iron content is related to meteorisation of iron minerals in pyroclastic
deposits. The high permeability of the non confined aquifers difficult the selection of sites for
waste disposal and restricts the exploitation of building materials (SERNAGEOMIN, 1998,
Antinao et al., 2000). Building materials comprise gravel and sand used for construction and
currently exploited without planned management. Locally, exploitation of sand and gravel
produce land use conflict with areas recommended for protection of groundwater.
OSORNO
Hidrogeology is the most relevant topic in the Osorno area. Geological units are mainly
represented by pre-last glacial cycle Quaternary glacial deposits including materials
representative of at least two glacial cycles. Also, a Quaternary pyroclastic-epiclastic complex
sequence is well represented in the complete area and minor Oligocene-Miocene marine
sedimentary rocks are also exposed in the western portions of the studied area. Glacial and
pyroclastic deposits are in general good enough for building foundations, except in flood areas,
specially along the main rivers.
Pérez et al. (2000) and Troncoso et al. (2000) conclude that the higher productivity aquifer is
located to a depth lower than 100 m in glacial deposits. Generally, as the aquifer is confine by
pyroclastic-epiclastic deposits, its vulnerability is low, except in sectors in which the confining
materials have been eroded. Also, less important non-confined aquifers in glacial and pyroclasticepiclastic deposits and in fractured rocks are respectively best represented in the southeastern and
northwestern portions of the studied area. As no other source for water supply was identified
nearby the northeastern portion, unconfined aquifers in fracture rocks could be taken as local
sources. In the eastern portion of the studied area, groundwater in unconfined aquifers shows
relatively high nitrate composition due to intense fertilisation of the land.
Building materials such as blocks, gravel and sand are extracted from fluvial and glaciofluvial
deposits. Clay minerals are exploited from altered pyroclastic materials and use to produce
bricks. Locally, exploitation of glaciofluvial deposits increases the vulnerability of aquifers
producing conflicts in land use. Also, due to eventual contamination of aquifers, location of
domestic and industrial waste disposals should be restricted in glaciofluvial deposits but
recommended in old glacial deposits (morraines) exposed in the central western portions of the
area.
VALDIVIA
Geological hazards are the most relevant topic in the Valdivia area. The geologic units include
glaciofluvial, estuarine, fluvial and coastal Quaternary deposits, continental and marine
sedimentary Miocene rocks, Cretaceous and early Tertiary plutons and Paleozoic-Triassic
metamorphic complex (SERNAGEOMIN, 1998, Duhart et al., 2001). The Cenozoic geological
history of the region is characterised by the development of a sedimentary basin partitioned into
several depocenters showing important tectonic control and successive uplifts and subsidence.
Arenas et al. (2002, 2003) conclude that the main geological hazards are earthquakes, landslides
and floods, the second one mainly associated to steep slopes in metamorphic rocks and the latter
due to tectonic subsidence, tsunamis and local high intensity rainfall (>50 mm/day), combined
with high tides. Historically, seismic events and related tsunamis have been catastrophic in the
region. Moreover, due to a rough topography urban areas are established in low lands, related to
tectonically controlled depocenters, with low quality foundation soils.
Aquifers from high to low importance were recognised in sedimentary deposits and metamorphic
and intrusive rocks. As shown by Arenas et al. (2002, 2003), the most productive and high-waterquality aquifers are within pyroclastic and sedimentary sequences belonging to the last
interglacial age, or in glaciofluvial deposits related to a previous glacial cycle, both showing low
to very low vulnerability depending on the thickness of the cover.
Industrial rocks are represented by schists and granodiorites locally extracted in quarries. Low
quality building materials include gravel, sand and clay, and are exploited in pits or from river
beds. In some cases, the extraction of rocks and building materials respectively produce
instability of slopes and conflicts with superficial and groundwater use.
DIFFUSION OF RESULTS
By means of diffusing the information in workshops and talks and spread of general written
information, local and regional authorities, local communities and communication agents have
got a basic degree of understanding of the importance of the environmental geology information,
specially about geological hazards, soils and groundwater. However, many important aspects of
communication and diffusion need to be improved in order to reach a better understanding and
application of the produced information.
The experiences in south central Chile show that language as simple and non-technical as
possible should be adopted in the maps and in the explanatory text. Also, a detailed programme
of communication, education and diffusion needs to be developed before, during and after the
development of any project relative to environmental geology for land use planning in any
particular area. This programme of communication, education and diffusion must be oriented to
both authorities with responsibility in land planning and to local leader and members of the
community, specially those members exposed to geological hazards.
For this purpose, the following three stages need to be formally completed during the diffusion
and education processes:
COMPILATION STAGE
Before starting the field work and during compilation of available data are necessary formal
exchanges of information with authorities and communities. Communication should also be
oriented to better define relevant topics and zones needing more detailed attention and work.
Communities and authorities need to be educated and informed about general aspects of
environmental geology, geological hazards and prevention and mitigation of natural events. Also,
all the involved parts must define and accepted a common language (i.e., hazard versus risk) and
the general scope and limitation of the planned work should be clearly explained. This could
include written information and talks about environmental geology and natural hazards (i.e.,
General Information Guide).
DEVELOPMENT STAGE
During the development of the work, authorities and communities need to continue their
education. They should receive and assume the preliminary information about results on local
geological hazards and zoning. Also, as a result of these conversations, new orientation to the
field work and data collection could be made. The written information and the preliminary results
are given to authorities in order to start planning on the prevention of possible local events (Local
Information Guide).
FOLLOW UP STAGE
Once the study has been completed all the information need to be formally delivered and clearly
explained to authorities and local communities, for example through local workshops and talks.
The clear and simple explanation of each treated topic and results, the potential use of the final
products and the necessary implementation of the recommendation are crucial for prevention and
mitigation planning. Authorities need to establish formal commitments with communities in
order to effectively assume the received information and to apply it in solving present day risk
conditions and during land use planning. All the results of the study must be summarised and
formally spread to authorities and local communities in a simple written format (Local Prevention
and Mitigation Guide).
Once the study is complete, the whole set of thematic maps should be published altogether with
the synthesis map and the explanatory text both in a paper and a digital CD format. Complete
printed set of maps is very expensive and could result in a limited distribution. Publication in a
CD format is cheaper and gives possibilities for a more massive distribution and diffusion of the
results of the studies.
CONCLUSIONS
Environmental geology for land use planning is an emergent branch of the geology in Chile. Its
development requires training of new experts in themes still not tried in the areas where studies
have been completed. Important advances have been obtained in geological hazard,
hydrogeology, vulnerability, building materials and application of geographical information
systems. However, soil mechanics, seismic response, applied geophysics, geochemistry, numeric
information and environmental protection has not been included in the already completed studies.
Also, national norms and standards need to be established for each one of the studied themes.
An organised programme of education and diffusion of the information must be oriented to local
authorities and communities. This action should be developed in three stages: before, during and
after completion of the study in any particular area. Local authorities and communities need to be
continuously educated and informed during these three stages in order to reach better results in
the application of the information.
AKNOWLEDGEMENTS
We thank SERNAGEOMIN-Chile and BGR-Germany for their support and financing of the
geologic environmental studies in south central Chile. Jorge Parra and Ignacio Bascuñan are
thanked for their support in producing the digital maps. Personnel from Oficina Técnica Puerto
Varas and Laboratory of SERNAGEOMIN made possible the field work and the analytical data,
respectively. Publication sponsored by the Subdirección Nacional de Geología,
SERNAGEOMIN.
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