GIS-Based Relief Compartment Mapping of Fluvio-Karst Landscape in Central Brazilian Highlands

The present study describes the preliminary findings of a research project aiming at creating a knowledge-base for the protection of caves heritage at Rio Vermelho preservation area in the central Brazilian highlands. A GIS-based relief compartment mapping was conducted using readily available data (e.g., satellite images, geological, and cave location maps). Four resultant geomorphological domains were identified, including (i) lowlands (282 km2) with a baselevel in silicates and carbonates, (ii) the karst terrains (994 km2) which were developed in carbonates trapped by siltstone lenses, (iii) the talus (1483 km2) having colluvial and alluvial units deposited by the escarpment retreat (Urucuia Formation) and (iv) the highlands (1143.7 km2) developed over the sandstone of the Urucuia Group. The intersection of landform and geological maps resulted in delineating two abrupt contacts, the first between lowland and karst terrains and the second between the talus and highlands that formed canyon escarpment. For sustainability perspective, this study proposed two types of cave systems in the region as superior/vadose (top-bottom) that collect floods from hillslopes and deep Epigene fluvial-karst (bottom-up)

Polavtomatski pristop za kartiranje vrtač na brazilskem pokritem krasu: pot do ocene ranljivosti

Doline mapping is paramount in the vulnerability and risk assessment of the underground karst environment by identifying cave-ground connectivity points at the surface. However, manual mapping is labour-intensive, slow and subjective, especially on a large scale. Therefore, the present study adopted a GIS-based semi-automatic approach for mapping large and medium-sized depressions/dolines in the Corrente river basin in Brazil, with a particular focus on the environmentally preserved areas of river Vermelho (APANRV Portuguese abbreviation) using remote sensing (DEM and Google Earth imagery) and field-based observations. Seven typical dolines forms (e.g., cockpit with drain insertion, collapse, collapse with river capture, suffosion, solution, cover collapse, and buried) are found from extensive field surveys. As an outcome of the proposed approach, two hundred and thirty-two medium to large-sized dolines have been identified and categorised into three main groups based on the cave density and local geology G1, G2, and G3. The high density of identified dolines (164 known caves) in G1 provides reconnaissance for future speleological works in the preserved areas. Additionally, the presence of a considerable number of dolines in the adjoining areas (G2 and G3) stresses the need to revise the existing boundaries of the APANRV. Results correlate well with the dolines sites marked using field surveys and Google Earth images. This doline mapping may help researchers in the groundwater vulnerability assessment and the protection of speleological heritage preserved in the caves.Kartiranje vrtač je nadvse pomembno za oceno ranljivosti in tveganja podzemnega kraškega okolja, saj določa točke povezanosti med jamami in tlemi na površju. Vendar je ročno kartiranje zelo zahtevno, časovno zamudno in subjektivno, zlasti v velikih merilih. Zato je bil v tej študiji uporabljen polavtomatski pristop z uporabo orodij GIS za kartiranje velikih in srednje velikih kraških globeli/vrtač v porečju reke Corrente v Braziliji s posebnim poudarkom na okoljsko ohranjenih območjih reke Vermelho (portugalsko APANRV) z uporabo daljinskega zaznavanja (posnetki DEM in programa Google Earth) in na podlagi terenskih opazovanj. Na podlagi obsežnih terenskih raziskav je ugotovljenih sedem značilnih oblik vrtač (npr. kokpit z drenažo, udornica, udornica z zajezitvijo reke, sufozija, škavnica, udornica, nastala z udorom/rušenjem jamskega stropa, in udornice, nastale z zasutjem). Kot rezultat predlaganega pristopa je bilo opredeljenih 232 srednje velikih do velikih vrtač, ki so bile glede na gostoto vrtač in lokalno geologijo razvrščene v tri glavne skupine G1, G2 in G3. Velika gostota opredeljenih vrtač (164 znanih jam) v skupini G1 zagotavlja predhodni pregled za prihodnja speleološka dela na ohranjenih območjih. Poleg tega prisotnost velikega števila vrtač na sosednjih območjih (G2 in G3) poudarja potrebo po ponovnem pregledu zdajšnjih meja APANRV. Rezultati se dobro ujemajo z lokacijami vrtač, kartiranimi na podlagi terenskih raziskav in posnetkov programa Google Earth. To kartiranje vrtač lahko raziskovalcem pomaga pri oceni ranljivosti podzemne vode in pri zaščiti speleološke dediščine, ohranjene v jamah

Reconhecimento geomorfológico de relevo cárstico sob rochas quartizíticas: bacia hidrográfica do Ribeirão Santana, médio vale do Rio Paraíba do Sul

Abstrac

Terra - feições ilustradas

Sem resumo no origina

ESTUDOS DOS CONTROLES MORFOMÉTRICOS A FEIÇÕES EROSIVAS E A IDENTIFICAÇÃO DE POSSÍVEIS ÁREAS SUSCEPTÍVEIS A MOVIMENTO DE MASSA NA BACIA HIDROGRÁFICA DO RIBEIRÃO CONTAGEM/DF

This work aims to create a morfometric analysis oriented to the catchment on the Contagem Basins/DF. We are trying to identify rates of erosion susceptibility from a hydro-geomorphologycal map proposal. The map were generate crossing the drainage efficiency index (DEI) and the morphological map (slope and curvature). We used the ArcMap 9.3 SIG to build Maps and create datas to made tables and graphs. Second order catchments have DEI (km/km²) values from 0,04to 18,56, with 4,51 of average. Third order catchments have values from 0,04to 18,56, with 2,48 of average. Near 80% of the features mapped by Braga (2012) were in the areas of DEI, because that map has covered the slope process mainly. The curvature map shows the concentration of the erosive features on the concave slopes, despite the fact that there are a majority of convex features, confirming expectations about the correlation of erosion and flow concentration. The hydro-geomorphological map showed areas of erosive susceptibility emphasizing the possible landslides areas. There are a low erosion potential in average, despites the fact that 49% were divided in medium and high erosion potential, which was not expected to a basin in Brasília. Landslides were observed in fieldworks, even if they have not been systematically mapped. The next steps of the work in the Contagem basin will focus on the landslides mapping and geotechnical resistance of the material.O objetivo deste trabalho é realizar uma análise morfométrica orientada a bacias hidrográficas na bacia hidrográfica do ribeirão da Contagem/DF, por meio do cruzando dos dados resultantes com o mapeamento de feições erosivas confeccionados por Braga (2012), buscando-se, assim, identificar unidades com diferentes susceptibilidades à erosão, com a confecção de proposta de mapeamento hidro-geomorfológico da bacia. O mapa hidro-geomorfológico da bacia foi gerado a partir do mapa de Índice de Eficiência de Drenagem (das bacias de segunda e terceira ordem), declividade e de curvatura (côncavo, retilíneo e convexo). Os dados foram elaborados e cruzados em Sistema de Informações Geográficas (ArcGis 9.3). Com relação ao mapa de Índice de Eficiência de Drenagem (IED) gerado a partir das bacias de segunda e terceira ordem, observou-se que as bacias de segunda ordem possuem valores de IED (km/km²) que variaram entre 0,0225 e 27,723, com média de 4,515284 (IED médio), enquanto as bacias de terceira apresentaram valores de IED (km/km²) entre 0,04 e 18,56, com média de 2,48 (IED baixo). Pelo fato do mapa IED ser formado por bacias de segunda e terceira ordens e essas estarem na escala dos processos geomorfológicos das encostas, o mapa abrangeu quase 80% das erosões existentes na bacia. A partir do mapa de curvatura, observou-se que as feições erosivas ficaram mais concentradas nas áreas côncavas das encostas. Apesar das formas convexas possuírem uma maior expressividade na bacia (46% da bacia é formada por regiões convexas), as feições ficaram mais concentradas nas regiões côncavas do relevo, provavelmente porque nas regiões côncavas há uma grande concentração de fluxo, o que pode contribuir no acontecimento de processos, pois estas possuem uma fragilidade ambiental maior. O mapa hidro-geomorfológico mostrou áreas de potencialidade erosivas, com ênfase nos movimentos de massa. Observou-se que a bacia estudada possui, no geral, um baixo potencial erosivo, havendo, porém, áreas de escarpa e encostas limítrofes ao canal principal com alto potencial erosivo e processos que incluem movimentos de massa. Futuros projetos podem ser feitos para mapear e estudar tais processos na bacia

Microtremor response of a mass movement in Federal District of Brazil

The present study provides a brief description of the ambient noise recorded at a slow moving mass movement in Ribeirão Contagem Basin. The area is an interesting natural laboratory as river detachment processes in a number of different stages can be identified and are easily accessible. We investigate the site dynamic characteristics of the study area by recording ambient noise time-series at nine points, using portable nine three-component short period seismometers. The time-series are processed to give both horizontal to vertical spectral ratio (HVSR) curves as well as time-frequency plots of noise power spectral density (SPD). The HVSR curves illustrate and quantify aspects of site resonance effects due to underlying geology. Probability density function (PDF) shows that noise level lies well between new high noise model (NHNM) and new lower noise model (NLNM) and their probabilities are higher above 2 Hz. HVSR curves present a uniform lithologically controlled peak at 2 Hz. Directional properties of the wavefield are determined by beamforming method. The f-k analysis results in the E-W component show that at 5 Hz phase velocities are close to 1700 m/s while at 10 Hz dropped to 250 m/s. We observed that between 5 and 16 Hz the incoming wavefield arrive from 260 degrees. Further studies will apply a detailed noise analysis for the understanding of dynamics of the mass movement, which is triggered by the river erosion

A semi-automatic approach for doline mapping in Brazilian covered karst: the way forward to vulnerability assessment

peer reviewedDoline mapping is paramount in the vulnerability and risk assessment of the underground karst environment by identifying cave-ground connectivity points at the surface. However, manual mapping is labour-intensive, slow and subjective, especially on a large scale. Therefore, the present study adopted a GIS-based semi-automatic approach for mapping large and medium-sized depressions/dolines in the Corrente river basin in Brazil, with a particular focus on the environmentally preserved areas of river Vermelho (APANRV Portuguese abbreviation) using remote sensing (DEM and Google Earth imagery) and field-based observations. Seven typical dolines forms (e.g., cockpit with drain insertion, collapse, collapse with river capture, suffosion, solution, cover collapse, and buried) are found from extensive field surveys. As an outcome of the proposed approach, two hundred and thirty-two medium to large-sized dolines have been identified and categorised into three main groups based on the cave density and local geology G1, G2, and G3. The high density of identified dolines (164 known caves) in G1 provides reconnaissance for future speleological works in the preserved areas. Additionally, the presence of a considerable number of dolines in the adjoining areas (G2 and G3) stresses the need to revise the existing boundaries of the APANRV. Results correlate well with the dolines sites marked using field surveys and Google Earth images. This doline mapping may help researchers in the groundwater vulnerability assessment and the protection of speleological heritage preserved in the caves

DISTRIBUIÇÃO ESPACIAL DE DEPRESSÕES NA BACIA DO ALTO RIO PRETO (GO, DF, MG) E SUAS RELAÇÕES COM CONTROLES GEOLÓGICOS E PEDOGEOMORFOLÓGICOS

O presente estudo tratou das feições doliniformes na bacia do alto rio Preto. De um total de 177 feições identificadas, a maioria está próxima ou conectada à drenagem, sendo menos circulares que outras identificadas como isoladas. Tais feições possuem agrupamentos nítidos e sua distribuição indica que são controladas por falhas associadas a dobras da Faixa de Dobramentos Brasília, diante da comparação de seus eixos de orientação com alinhamentos geológicos. Foi observado que 90% das depressões se assentam sobre as rochas carbonáticas do Grupo Bambuí.</p

MAPEAMENTO DE FEIÇÕES EROSIVAS E ANÁLISE DOS FATORES CONTROLADORES DA EROSÃO NA BACIA HIDROGRÁFICA DO RIBEIRÃO CONTAGEM (DF)

This work aims to study the correlations between erosion features as gullies and channels with controls as roads, lithology, soil type and slope on Contagem basin, north region of Federal Disctrict/Brazil. Channels and features was mapped in a 1:10.000 scale base, with aerial photos and curves, in a GIS environment. Was generated Terrain Digital models and morphometric maps. The data were crossed in GIS environment using ArcGis 9.3. The results shown 3777 channels, 78% more than the older map (Terracap, 2010); and, 233 features, 100% more than the older map (Oliveira, 2011). The main controls was found between phyllite and gullies; means inverse relanshiship with vegetation density, concentration of features in high slopes (&gt; 35 °) and correlation between channels and features. The results suggest widespread adjustment slope, controlling headward erosion and gullies formation (n=90), unsettle or not by road construction.O estudo objetivoudemonstrar os controles que a litologia, pedologia, vegetação, declividade e proximidade de canais e estradas podem exercer para o desenvolvimento de feições erosivas na bacia hidrográfi ca do Ribeirão Contagem, norte do Distrito Federal/Brasil. Foram mapeados canais e feições erosivas em ortofotocartas na escala 1:10.000, com posterior elaboração de Modelos Digitais do Terreno, morfometrias e elaboração e cruzamento dos dados em ambiente SIG, utilizando ArcGis9.3. O mapeamento resultou em 3777 canais e adensamento de 78% em relação a mapeamentos anteriores (Terracap, 2010), e 233 feições erosivas e adensamento de 100% em relação a outros mapeamentos(Oliveira, 2011). Os principais controles são entre feições e a litologia clorita fi litos; relação inversa entre distribuição de feições e densidade vegetacional; concentração de feições em baixas declividades; e, correlação entre canais e feições. Os resultados obtidos sugerem que as feições erosivas do tipo voçorocas (n.=90) estão evoluindo a partir do crescimento remontante da rede de canais por ajuste de declives

Microtremor Response of a Mass Movement in Federal District of Brazil

The present study provides a brief description of the ambient noise recorded at a slow moving mass movement in Ribeirão Contagem Basin. The area is an interesting natural laboratory as river detachment processes in a number of different stages can be identified and are easily accessible. We investigate the site dynamic characteristics of the study area by recording ambient noise time-series at nine points, using portable nine three-component short period seismometers. The time-series are processed to give both horizontal to vertical spectral ratio (HVSR) curves as well as time-frequency plots of noise power spectral density (SPD). The HVSR curves illustrate and quantify aspects of site resonance effects due to the local geological setting. Probability density function (PDF) shows that noise level lies well between new high noise model (NHNM) and new lower noise model (NLNM) and their probabilities are higher above 2 Hz. HVSR curves present a uniform lithologically controlled peak at 2 Hz. Directional properties of the wavefield are determined by beamforming method. The f-k analysis results in the E-W component show that at 5 Hz phase velocities are close to 1700 m/s while at 10 Hz dropped to 250 m/s. We observed that between 5 and 16 Hz the incoming wavefield arrive from 260 degrees. Further studies will apply a detailed noise analysis for relating the dynamics of the landslide (which can be retriggered by river erosion as well as rainfalls and seismic shaking) to possible changes in detectable physical properties