Global riverine flood risk – how do hydrogeomorphic floodplain maps compare to flood hazard maps?

Riverine flood risk studies often require the identification of areas prone to potential flooding. This modelling process can be based on either (hydrologically derived) flood hazard maps or (topography-based) hydrogeomorphic floodplain maps. In this paper, we derive and compare riverine flood exposure from three global products: a hydrogeomorphic floodplain map (GFPLAIN250m, hereinafter GFPLAIN) and two flood hazard maps (Flood Hazard Map of the World by the European Commission's Joint Research Centre, hereinafter JRC, and the flood hazard maps produced for the Global Assessment Report on Disaster Risk Reduction 2015, hereinafter GAR). We find an average spatial agreement between these maps of around 30 % at the river basin level on a global scale. This agreement is highly variable across model combinations and geographic conditions, influenced by climatic humidity, river volume, topography, and coastal proximity. Contrary to expectations, the agreement between the two flood hazard maps is lower compared to their agreement with the hydrogeomorphic floodplain map. We also map riverine flood exposure for 26 countries across the global south by intersecting these maps with three human population maps (Global Human Settlement population grid, hereinafter GHS; High Resolution Settlement Layer, hereinafter HRSL; and WorldPop). The findings of this study indicate that hydrogeomorphic floodplain maps can be a valuable way of producing high-resolution maps of flood-prone zones to support riverine flood risk studies, but caution should be taken in regions that are dry, steep, very flat, or near the coast.

Geographic and Temporal Access to Basic Banking Services Offered through Post Offices in Wales

Access to ‘universal banking services’ through the post office network has been a goal of the UK governments over the last twenty years. Various policies and mechanisms have been put in place in an attempt to maintain national geographical coverage with access points while increasing the financial viability of the network. One such mechanism is represented by the six official criteria for access to post offices, expressed as a percentage of the UK population living within one mile, three miles, and six miles of a post office. The method for calculating compliance with these access criteria is not published. Nor will any granular results be published, but only an annual statement that the criteria are being met. This article examines geographical and temporal access to post offices in order to understand the territorial coverage of the network and the impact this has on the provision of basic banking services. The area under investigation is Wales, for which we are reviewing the Government’s official access criteria. Through the Post Office Ltd website, we are collecting up-to-date information on the locations and opening hours of post offices in Wales. In addition, a detailed population grid is combined with calculated areas of equidistant geographical access, called isochrones, to determine the number of people who have access to the post office network. The isochrones are based on the Welsh road network and are calculated for different travel modes and thresholds using a powerful routing engine. Our results show that the official access criteria are largely unmet in Wales. In addition, and in contrast to previous studies, we show a rural-urban divide not in terms of spatial access, but in the combination of spatial and temporal access. The results are of both practical and theoretical value and will hopefully inform policy makers.

The spatial distribution of population in Spain: An anomaly in European perspective

We exploit the GEOSTAT 2011 population grid to document that Spain presents the lowest density of settlements among European countries. Only a small fraction of the Spanish territory is inhabited, particularly in its southern half, which goes hand in hand with a high degree of population concentration. We uncover through standard regression analysis and spatial regression discontinuity that this anomaly cannot be accounted for by adverse geographic and climatic conditions. The second part of the paper takes a historical perspective on Spain's settlement patterns by showing that the spatial distribution of the population has been very persistent in the last two centuries, and that the abnormally low density of settlements with respect to European neighbors was already visible in the 19th century, which indicates that this phenomenon has not emerged recently as a consequence of the transformations associated with industrialization and tertiarization. Using data on ancient sites, we find that Spain did not feature scarcity of settlements in comparison to other countries in pre-medieval times, suggesting that its current anomalous settlement pattern has not always existed and is therefore not intrinsic to its geography.

Racial dot maps based on dasymetrically modeled gridded population data

Racial geography - mapping spatial distributions of different racial groups is of keen interest in a multiracial society like the United States. Racial dot map is a method of visualizing racial geography which depicts spatial distribution, population density, and racial mix in a single, easy-to-understand map. Because of the richness of information it carries, the dot map is an excellent tool for visual analysis of racial distribution. Presently used racial dot maps are based on the census data at the tract or the block level. In this paper, we present a method of constructing a more spatially accurate racial dot map based on a sub-block resolution population grid. The utility of our dot maps is further enhanced by placing dots on the map in random order regardless of the race they represent in order to achieve a more accurate depiction of local racial composition. We present a series of comparisons between dot maps based on tract, block, and grid data. The advantage of a grid-based dot map is evident from the visual comparison of all maps with an actual image of the mapped area. We make available the R code for constructing grid-based dot maps. We also make available 2010 grid-based racial dot maps for all counties in the conterminous United States.

Monitoring of UN sustainable development goal SDG-9.1.1: study of Algerian “Belt and Road” expressways constructed by China

The proportion of the rural population who live within 2 km of an all-season road is an indicator of the United Nations’ Sustainable Development Goals (SDGs) 9.1.1. This paper aims to calculate SDG indicator 9.1.1 in the proximity of five Algerian expressways. Three monitoring methods are proposed for different spatial regions based on the five expressways built by China’s Belt and Road Initiative Project. These methods are based on remote sensing and WorldPop and The High Resolution Settlement Layer (HRSL) population data. The results indicate that (1) the WorldPop population statistics show that the five expressways built by China’s Belt Project have increased the rural population of the 2 km buffer zone by 192,016 between the start of construction and eight years after its completion. By the end of 2019, the population increased by 329,291 accounting for 1.17% of the rural population. (2) Based on populations estimated form built-up index (NDBI) building areas, the rural populations within the 2 km buffer area of the Bejaia-Haniff Expressway in 2011, 2015, and 2019 were 273,118, 306,430, and 375,408, respectively. (3) HRSL population grid statistics indicate that, in 2015, the populations were: East-West Expressway = 911,549, Bejaia Expressway = 127,471, Tipaza Expressway = 71,411, North-South Expressway = 30,583, and Cherchell Ring Expressway = 41,657. (4) A visual interpretation method based on Google Earth imagery was used to count the number of buildings and number of building floors in the town of Tikhramtath. Based on the estimated population of each building and floor, the population of Tikhramtath town in 2011, 2015, 2017, and 2019 was estimated as 1,790, 2,785, 3,365, and 3,870, respectively. (5) Through analysis and accuracy assessment, the appropriate statistical methods for different regions were determined.

Immigrants in large Czech cities 2008–2015: the analysis of changing residential patterns using population grid data

This article contributes to the discussion of the segregation of immigrants by presenting evidence from a new destination country of international migration. It explores residential patterns of immigrants, defined by citizenship, and their development in selected large Czech cities. The analysis is focused on six main immigrant groups. New register data provided by Alien Police of the Czech Republic are utilized for the computation of geospatial grid data. The changes in population distribution are measured by the dissimilarity index, which is commonly used in segregation research. The main result indicates a major trend of decreasing spatial dissimilarity between the Czech majority and immigrant groups. The steady and slow inflow of immigrants does not lead to distinct patterns of segregation in the country – with a few specific exceptions.

Changes of Population, Built-up Land, and Cropland Exposure to Natural Hazards in China from 1995 to 2015

By using the latest China population grid and land-use data, we assess the changing exposure of China’s population and land uses to the hazards of storm surges, droughts, earthquakes, floods, and landslides from 1995 to 2015. We found that the single-hazard areas and the multi-hazard areas covered 43% and 26% of China’s territory, respectively. Population grew faster in the hazard-prone areas than in the non-hazard areas. Built-up area expanded more rapidly in the areas prone to earthquakes and landslides. Cropland changed rapidly in many hazard-prone areas. The hazard-prone areas affected by floods featured the highest cropland loss rates, while the areas prone to earthquakes and landslides featured the highest cropland growth rates. We detected areas with significant exposure changes by using hot spot analysis. It was found that population and built-up land in the Pearl River Basin were increasingly exposed to storm surges, floods, and landslides. The Haihe River Basin and Huaihe River Basin also showed a consistent increase of population and built-up land exposure to droughts and earthquakes. These findings can provide a foundation for the design and implementation of protection and adaptation strategies to improve the resilience of Chinese society to natural hazards.

Missing millions: undercounting urbanization in India

The measurement and characterization of urbanization crucially depends upon defining what counts as urban. The government of India estimates that only 31% of the population is urban. We show that this is an artifact of the definition of urbanity and an underestimate of the level of urbanization in India. We use a random forest-based model to create a high-resolution (~ 100 m) population grid from district-level data available from the Indian Census for 2001 and 2011, a novel application of such methods to create temporally consistent population grids. We then apply a community-detection clustering algorithm to construct urban agglomerations for the entire country. Compared with the 2011 official statistics, we estimate 12% more of urban population, but find fewer mid-size cities. We also identify urban agglomerations that span jurisdictional boundaries across large portions of Kerala and the Gangetic Plain.