Hazards (Geography)

Hurricane Katrina as a Lens for Assessing Socio-Spatial Change in New Orleans (2011)

by Case Watkins

Based on my master's thesis and co-authored with my MA advisor, Ron Hagelman. Published in Southeastern Geographer, Volume 51, Number 1, Spring 2011, pp. 110-132, and available on Project Muse.

http://muse.jhu.edu/journals/sgo/v051/51.1.watkins.html

Please e-mail me for a copy if your institution does not have access.

Abstract:

Disasters are acute events that affect populated landscapes at discrete points in their history.... more Abstract:

Disasters are acute events that affect populated landscapes at discrete points in their history. In many locations, these discrete events occur repeatedly over time. This chronology has chorological implications in that one generation's disaster reconstruction zone could be the next generation's disaster site. This build-disaster-rebuild approach also occurs within the context of changing social and environmental conditions, the interactions of which have direct implications to the outcome of a specific disaster event. This research focuses on the changing social geography of a large urban disaster site (New Orleans, Louisiana) by employing the U.S. Census, digital inundation data, and a GIS to conduct a spatial analysis of flood patterns during Hurricane Katrina. Following the initial analysis, we replicate our methodology across the three decennial census periods prior to 2000. While the initial analysis discerns the statistical relationship among race, income, and Katrina's deluge, the subsequent temporal analysis illuminates the changing social patterns that preceded the Katrina-era landscape. In this manner, we use hurricane inundation as a lens to view 35 years of socio-spatial change in New Orleans.

Resumen:

Los desastres son eventos agudos que afectan paisajes poblados en puntos discretos de su historia. En muchos lugares estos eventos discretos se producen repetidamente en el tiempo. Esta cronología tiene implicaciones corológicas en esa zona de reconstrucción de desastres de esa generación que podría ser el lugar de catástrofe de la próxima generación. Este enfoque de construcción-reconstrucción de desastres también se produce en el contexto de las cambiantes condiciones sociales y ambientales, de las cuales interacciones tienen implicaciones directas para el resultado de un desastre específico. Esta investigación se enfoca en la cambiante geografía social de un lugar de gran catástrofe urbana (Nueva Orleans, Louisiana), utilizando el Censo de los EE.UU., los datos digitales de inundación, y un SIG para llevar a cabo un análisis espacial de los patrones de las inundaciones durante el huracán Katrina. Siguiendo el análisis inicial, replicamos nuestra metodología en los tres períodos censales decenales anteriores al 2000. Si bien el análisis inicial discierne la relación estadística entre raza, ingreso, y el fenómeno de Katrina, el análisis temporal posterior acentúa los cambiantes patrones sociales que precedieron el paisaje de la era de Katrina. De esta manera, utilizamos las inundaciones del huracán como un lente para ver 35 años de cambio socio-espacial en Nueva Orleans.
Keywords:

Hurricane Katrina, New Orleans, Historical Geography, Socio-Spatial Change

Through the Lens of Katrina: A Historical Geography of the Social Patterns of Flood Exposure in New Orleans, 1970-2005

by Case Watkins

M.S. Thesis (Geography), Texas State University, 2008. Ronald R. Hagelman, III, advisor.

Two and a half years after Hurricane Katrina, its reverberations remain evident in New Orleans and throughout the... more Two and a half years after Hurricane Katrina, its reverberations remain evident in New Orleans and throughout the academic literature. Although scholars have written extensively on apparent social inequities present in the city before, during, and after the storm, an empirical consensus on the racial and socioeconomic distributions of the population relative to Katrina-induced flooding remains elusive. In response to this lacuna, I employ the U.S. Census, digital inundation data, and a GIS to analyze New Orleans' racial and socioeconomic geographies as they related to patterns of flood inundation in the city during the storm. Katrina’s inundation, however, represents only a brief episode within the greater history of New Orleans. While a temporally isolated analysis of a distinctive hazard event such as Katrina can be informative in and of itself, it does little to illuminate the evolution of the social landscape before or after the storm. Therefore, after conducting the initial analysis, I then replicate the methodology across the three decennial census periods prior to 2000 (1970, 1980, and 1990). While the initial assessment discerns the statistical relationship among race, socioeconomics, and Katrina’s inundation, the subsequent temporal analysis illuminates the historical patterns of social change that led to the landscape of exposure wrought by the storm in 2005. In essence, this research asks, "If Hurricane Katrina struck in 1970, 1980, or 1990, how, if at all, would the socioeconomic or racial geographies of flood exposure evident during each period differ from the patterns evident during the actual event in 2005?" I use Katrina’s inundation, then, as a lens through which we can view 35 years of urban social changes in New Orleans. I contend that it is not enough to understand merely whom the storm affected. Rather, scholars, managers, and policymakers at every level benefit by recognizing the evolution (or devolution) of social landscapes into those ripe for human disaster.

Geomorphic and hazard vulnerability assessment of recent residential developments on landslide-prone terrain: The case of the Traverse Mountains, Utah, …

by Kathleen Nicoll

--> Cite as: Nicoll, Kathleen, 2010. Geomorphic and hazard vulnerability assessment of recent residential developments on landslide-prone terrain: The case of the Traverse Mountains, Utah, USA. Journal of Geography and Regional Planning Vol. 3(6), pp. 126-141. Available online at http://www.academicjournals.org/JGRP/PDF/pdf2010/Jun/Nicoll.pdf

ABSTRACT Homeowners who live near or on steep slopes of the Traverse Mountains along the Wasatch front in southern... more ABSTRACT Homeowners who live near or on steep slopes of the Traverse Mountains along the Wasatch front in southern Salt Lake City, Utah (USA) are at risk where development of “master-planned communities” has been permitted on known landslide deposits since 2001. Some of the largest landslides in the state of Utah are being modified as road construction and residential development progresses. This paper reviewed the setting of the landslide-prone areas and used Geographic Information Systems (GIS) spatial tools to assess the value of local developments built on mapped slide features. Dataset overlays
were compiled to determine the vulnerability of residences, and to quantify potential monetary loss from a future landslide event. The key elements at risk include property, as well as the population, economic activities, and public services of a given region. An initial conservative figure calculated for the vulnerability of residents owning property exceeds $500 million for the Traverse Mountains region of Draper City, based on 2007 property values recorded at the Salt Lake County Assessors Office. In developing this area, the failure to consider existing and potential hazards has caused a myriad of tensions among local government officials, planners, financiers, state regulators, consultants, developers, realtors, and homeowners.

Writing on the plywood: Toward an analysis of hurricane graffiti

by Derek Alderman

Alderman, Derek H. and Heather Ward. 2008. “The Writing on the Plywood: Toward an Analysis of Hurricane Graffiti.” Coastal Management 36(1): 1-18. Recipient of 2010 Urban Communication Foundation Journal Article Award.

Modelling shallow landsliding susceptibility by incorporating heavy rainfall statistical properties

by Paolo Tarolli

Published in Geomorphology, 2011. Co-authored with Marco Borga, Kang-Tsung Chang, Shou-Hao Chiang

We present an index-based shallow landsliding susceptibility model which allows explicit incorporation of local heavy... more We present an index-based shallow landsliding susceptibility model which allows explicit incorporation of local heavy rainfall statistical properties. The model, called Quasi-Dynamic Shallow Landsliding Model (QD-SLaM), is developed upon a theory for coupled shallow subsurface flow and landsliding of the soil mantle. The model uses a 'quasi-dynamic' wetness index to predict the spatial distribution of soil saturation in response to a rainfall of specified duration, and can take into account the spatial variability of soil properties. The rainfall predicted to cause instability in each topographic element is characterized by intensity and duration. The incorporation of a scaling model for the rainfall frequency-duration relationship provides a parsimonious and robust way to include heavy rainfall statistical properties into shallow landsliding modelling. The model is used to determine the return period of the critical rainfall needed to cause instability for each topographic element. The model is validated over six different study sites, where detailed inventories of shallow landslides are available. Two study sites are located in the north of Taiwan, and four are located in the Italian Alps. The sites are characterized by different climates and by different duration of the landslide-triggering storms. Model results are evaluated against the surveyed landslides and compared to those obtained by using a steady-state model, resembling SHALSTAB. It is shown that QD-SLaM improves significantly over the steady-state approach in predicting existing landslides as represented in the considered landslide inventory. Moreover, the improvement is higher for the cases where the landslide-triggering storm duration is short with respect to the length of time required for every point on a catchment to reach subsurface drainage equilibrium. The results of our work highlight the capability of the model to incorporate a robust description of the heavy rainfall properties in the analysis and mapping of shallow landsliding susceptibility by using an index-style approach.

A New Method for Determination of Most Likely Landslide Initiation Points and the Evaluation of Digital Terrain Model Scale in Terrain Stability Mapping

by Paolo Tarolli

Published in HESS, 2006. Co-authored with D.G. Tarboton

This paper introduces a new approach for determining the most likely initiation points for landslides from potential... more This paper introduces a new approach for determining the most likely initiation points for landslides from potential instability mapped using a terrain stability model. This approach identifies the location with critical stability index from a terrain stability model on each downslope path from ridge to valley. Any measure of terrain stability may be used with this approach, which here is illustrated using results from SINMAP, and from simply taking slope as an index of potential instability. The relative density of most likely landslide initiation points within and outside mapped landslide scars provides a way to evaluate the effectiveness of a terrain stability measure, even when mapped landslide scars include run out zones, rather than just initiation locations. This relative density was used to evaluate the utility of high resolution terrain data derived from airborne laser altimetry (LIDAR) for a small basin located in the Northeastern Region of Italy. Digital Terrain Models were derived from the LIDAR data for a range of grid cell sizes (from 2 to 50 m). We found appreciable differences between the density of most likely landslide initiation points within and outside mapped landslides with ratios as large as three or more with the highest ratios for a digital terrain model grid cell size of 10 m. This leads to two conclusions: (1) The relative density from a most likely landslide initiation point approach is useful for quantifying the effectiveness of a terrain stability map when mapped landslides do not or can not differentiate between initiation, runout, and depositional areas; and (2) in this study area, where landslides occurred in complexes that were sometimes more than 100 m wide, a digital terrain model scale of 10 m is optimal. Digital terrain model scales larger than 10 m result in loss of resolution that degrades the results, while for digital terrain model scales smaller than 10 m the physical processes responsible for triggering landslides are obscured by smaller scale terrain variability

Analyzing the influence of upslope bedrock outcrops on shallow landsliding

by Paolo Tarolli

Published in Geomorphology, 2008. Co-authored with Marco Borga and Giancarlo Dalla Fontana

A model for the prediction of topographic and climatic control on shallow landsliding in mountainous terrain is... more A model for the prediction of topographic and climatic control on shallow landsliding in mountainous terrain is enhanced to analyse the impact of upslope rocky outcrops on downslope shallow landsliding. The model uses a ‘generalised quasi-dynamic wetness index’ to describe runoff propagation on bare rock surfaces connected to downslope soil-mantled topographic elements. This approach yields a simple enhanced model capable of describing the influence of upslope bedrock outcrops on the pattern of downslope soil saturation. The model is applied in both diagnostic and predictive modes to a small catchment in the eastern Italian Alps for which a detailed inventory of shallow landslides in areas dominated by rocky outcrops is available. In the diagnostic mode, the model is used with satisfactory results to reproduce the pattern of instability generated by an intense short-duration storm occurred on 14 September 1994, which triggered a large percentage of the surveyed landslides. In the predictive mode, the model is used for hazard assessment, and the return time of the critical rainfall needed to cause instability for each topographic element is determined. Modelling results obtained in the predictive mode are evaluated against all the surveyed landslides. It is revealed that the generalised quasi-dynamic model offers considerable improvement over the non-generalised quasi-dynamic model and the steady-state model in predicting existing landslides as represented in the considered landslide inventory.

Geomorphic features extraction from high-resolution topography: landslide crowns and bank erosion

by Paolo Tarolli

Published in Natural Hazards, 2012. Co-authored with Giulia Sofia, Giancarlo Dalla Fontana

In recent years, new remote-sensed technologies, such as airborne and terrestrial laser scanner, have improved the... more In recent years, new remote-sensed technologies, such as airborne and terrestrial laser scanner, have improved the detail and the quality of topographic information, providing topographical high-resolution and high-quality data over larger areas better than other technologies. A new generation of high-resolution (<3 m) digital terrain models (DTMs) is now available for different areas and is widely used by researchers, offering new opportunities for the scientific community. These data call for the development of a new generation of methodologies for an objective extraction of geomorphic features, such as channel heads, channel networks, bank geometry, debris-flow channel, debris-flow deposits, scree slope, landslide and erosion scars, etc. A high-resolution DTM is able to detect the divergence/convergence of areas related to unchannelized/channelized processes with better detail than a coarse DTM. In this work, we tested the performance of new methodologies for an objective extraction of geomorphic features related to shallow landsliding processes (landslide crowns), and bank erosion in a complex mountainous terrain. Giving a procedure that automatically recognizes these geomorphic features can offer a strategic tool to map natural hazard and to ease the planning and the assessment of alpine regions. The methodologies proposed are based on the detection of thresholds derived by the statistical analysis of variability of landform curvature. The study was conducted on an area located in the Eastern Italian Alps, where an accurate field survey on shallow landsliding, erosive channelized processes, and a high-quality set of both terrestrial and airborne laser scanner elevation data is available. The analysis was conducted using a high-resolution DTM and different smoothing factors for landform curvature calculation in order to test the most suitable scale of curvature calculation for the recognition of the selected features. The results revealed that (1) curvature calculation is strongly scaledependent, and an appropriate scale for derivation of the local geometry has to be selected according to the scale of the features to be detected; (2) such approach is useful to automatically detect and highlight the location of shallow slope failures and bank erosion, and it can assist the interpreter/operator to correctly recognize and delineate such phenomena. These results highlight opportunities but also challenges in fully automated methodologies for geomorphic feature extraction and recognition.

Hillslope-to-valley transition morphology: new opportunities from high resolution DTMs

by Paolo Tarolli

Published in Geomorphology, 2009. Co-authored with Giancarlo Dalla Fontana

The search for the optimal spatial scale for observing landforms to understand physical processes is a fundamental... more The search for the optimal spatial scale for observing landforms to understand physical processes is a fundamental issue in geomorphology. Topographic attributes derived from Digital Terrain Models (DTMs) such as slope, curvature and drainage area provide a basis for topographic analyses. The slope–area relationship has been used to distinguish diffusive (hillslope) from linear (valley) processes, and to infer dominant sediment transport processes. In addition, curvature is also useful in distinguishing the dominant landform process. Recent topographic survey techniques such as LiDAR have permitted detailed topographic analysis by providing high-quality DTMs. This study uses LiDAR-derived DTMs with a spatial scale between 1 and 30 m in order to find the optimal scale for observation of dominant landform processes in a headwater basin in the eastern Italian Alps where shallow landsliding and debris flows are dominant. The analysis considered the scaling regimes of local slope versus drainage area, the spatial distribution of curvature, and field observations of channel head locations. The results indicate that: i) hillslope-to-valley transitions in slope–area diagrams become clearer as the DTM grid size decreases due to the better representation of hillslope morphology, and the topographic signature of valley incision by debris flows and landslides is also best displayed with finer DTMs; ii) regarding the channel head distribution in the slope–area diagrams, the scaling regimes of local slope versus drainage area obtained with grid sizes of 1, 3, and 5 m are more consistent with field data; and iii) the use of thresholds of standard deviation of curvature, particularly at the finest grid size, were proven as a useful and objective methodology for recognizing hollows and related channel heads.

Understanding earth surface processes from remotely sensed digital terrain models

by Paolo Tarolli

Published in Geomorphology, 2009. Co-authored with J Ramon Arrowsmith and Enrique Vivoni

This special issue brings together studies on the innovative use of remotely sensed DTMs for Earth science... more This special issue brings together studies on the innovative use of remotely sensed DTMs for Earth science applications for obtaining new understanding of earth surface processes. The idea for this issue arose from a session on “Remotely sensed DTM for Hydrogeomorphic Applications” convened the proponents as well as William E. Dietrich and Salvatore Grimaldi, during the 2007 Annual Fall Meeting of the American Geophysical Union, held in San Francisco, California. The three oral and one poster sessions attracted 41 abstracts from North America, Europe and Asia, providing an opportunity to review methods, discuss challenges, and evaluate recent technological advances in the use of remotely sensed topographic data for Earth surface processes. Some of the posters and presentations discussed during the meeting sessions were developed into the papers appearing in this special issue. Our goal is to share advances in landscape analysis that are significantly improved by the use of different remotely sensed data sets.We decided to consider a range of remotely sensed technologies in order to offer the scientific community different options and perspectives from recent work. The sequence of contributions is arranged according to the spatial characteristics of the techniques and methods concerned: from very high resolution data collected by TLS, to a progressively coarser resolution data from LiDAR, STRM, and ASTER remotely sensed technology

Testing space-scale methodologies for automatic geomorphic feature extraction from LiDAR in a complex mountainous landscape

by Paolo Tarolli

Published in Water Resources Research, 2010. Co-authored with Paola Passalacqua, Efi Foufoula-Georgiou

The next generation of digital elevation data (≤ 3m resolution)
calls for the development of new algorithms for... more The next generation of digital elevation data (≤ 3m resolution)
calls for the development of new algorithms for the objective extraction of geomorphic features, such as channel networks, channel heads, bank geometry, landslide scars, service roads, etc. In this work, we test the performance of two newly developed algorithms for the extraction of geomorphic
features: the wavelet-based extraction methodology developed by Lashermes et al. [2007] and the GeoNet-nonlinear diffusion and geodesic pathsmethodology proposed by Passalacqua et al. [2010]. The study area is part of the Rio Cordon basin, a headwater alpine catchment located in the Dolomites, a mountainous region in the Eastern Italian Alps. The aim of this work is to compare the capability of the two new algorithms in extracting the channel network, capturing channel heads, relevant channel disruptions corresponding to landslides, and representative channel cross-sections. The extracted
channel networks are also compared to the ones obtained using classical methodologies based on an area threshold and an area-slope threshold. A high resolution Digital Terrain Model (DTM) of 1 m served as the basis for such analysis. The results suggest that, although the wavelet-based methodology performs well in the channel network extraction and is able to detect channel heads and channel disruptions, the local nonlinear filter together with the global geodesic optimization used in GeoNet is more robust and computationally efficient, while achieving better localization and extraction of features,
especially in areas where gentle slopes prevail. We conclude that these new methodologies should be considered as valid alternatives to classical methodologies for channel network extraction from lidar, in addition to offering the potential for calibration-free channel source identification and also extraction of additional features of interest.

Considerações sobre Riscos Naturais num Espaço de Transição: Exercícios Cartográficos numa área a Sul de Coimbra

by Lúcio Cunha

L. Cunha e L. Dimuccio (2002) – “Considerações sobre riscos naturais num espaço de transição. Exercícios cartográficos numa área a Sul de Coimbra”. Territorium, Coimbra, 9, pp. 37-51.

Resumo:
Após algumas considerações sobre riscos naturais na área de Coimbra, pretende-se explorar as... more Resumo:
Após algumas considerações sobre riscos naturais na área de Coimbra, pretende-se explorar as potencialidades dos Sistemas de Informação Geográfica (SIG’s) para modelizar e cartografar o risco de movimentos de materiais em vertentes numa pequena área a Sul da cidade.

Résumé:
Après quelques considérations autour des risques naturels dans la région Coimbra, nous projetons d'explorer les potentialités des Systèmes d’Information Géographique( SIG’s) afin de modeler et de cartographier les mouvements de versant dans une petite région au sud de la ville.

Abstract:
After some considerations about natural risks in the Coimbra area, we intend to explore the Geographic Information System (GIS) potentialities for modelling and mapping slope movements
at a small south area of the town.