Hybrid infrastructures, hybrid governance: New evidence from Nairobi (Kenya) on green-blue-grey infrastructure in informal settlements: "Urban hydroclimatic risks in the 21st century: Integrating engineering, natural, physical and social sciences to build resilience” Publication date: January 2020 Source: Anthropocene, Volume 29 Author(s): Joe Mulligan, Vera Bukachi, Jack Campbell Clause, Rosie Jewell, Franklin Kirimi, Chelina Odbert Abstract In expanding informal neighborhoods of cities in sub-Saharan Africa, sustainable management of storm and wastewater drainage is fundamental to improving living conditions. Planners debate the optimal combination between "green" or natural infrastructure, traditional "grey" infrastructure, and "blue" infrastructure, which mimics natural solutions using artificial materials. Many advocate for small-scale, niche experiments with these approaches in informal settings, in order to learn how to navigate the intrinsic constraints of space, contested land tenure, participation, and local maintenance. This paper reports the benefits and limitations of implementing and managing local green, blue and grey infrastructure solutions in an urban informal setting. We studied ten completed public space projects that featured urban drainage infrastructure in the informal neighborhood of Kibera, Nairobi. The analysis drew from ten surveys with project designers and seven semi-structured interviews with site managers. The studied spaces featured different combinations of green, grey, and blue drainage infrastructure that have evolved over years of operation, maintenance, and change in the settlement. All projects featured participation in design, mixed design methods, hybrid infrastructure, and community governance models with potential to interact successfully with municipal actors. Results show that involvement in the co-development of small-scale green infrastructure changed people's valuation, perception, and stewardship of nature-based systems and ecosystem services. These results have implications for the larger scale adoption, integration, and management of urban drainage infrastructure. They also suggest that hybrid systems of infrastructure and governance constitute a resilient approach to incremental and inclusive upgrading.

Multiscalar spatial analysis of urban flood risk and environmental justice in the Charlanta megaregion, USA Publication date: December 2019 Source: Anthropocene, Volume 28 Author(s): Neil Debbage Abstract Previous research exploring the environmental justice implications of urban flood hazards has produced contrasting results due to the different dasymetric mapping techniques used, the various spatial scales of the analyses, and the specific geographical context of the individual study cities, particularly as it relates to the presence of coastal water-based amenities. To better understand if vulnerable populations are disproportionately exposed to urban flood hazards in non-coastal cities, this study assessed the magnitude of socio-economic inequities in flood risk throughout the Charlanta megaregion. Specifically, population characteristics within the 500-year flood zone were estimated using United States Census Bureau data for race, ethnicity, and poverty by applying three dasymetric mapping techniques at four spatial scales. Risk ratios were used to statistically evaluate if vulnerable populations were overrepresented in areas at risk for flooding overall as well as for lake and non-lake regions. Although the results varied according to the scale and socio-economic variable, the most accurate dasymetric mapping approach indicated that environmental injustices were systemic, as vulnerable individuals were between 14% and 42% more likely to reside in areas at risk for flooding when analyzing the entire megaregion. At the metropolitan scale, vulnerable individuals were still significantly more likely to reside in flood zones, and the influence of lake amenities on the disparities was nuanced. A complex spatial landscape of inequities was also observed at the county and census tract levels. Overall, the notable disparities faced particularly by non-Hispanic black and Hispanic populations suggest that urban flood risk inequities in the megaregion are largely due to structural forms of discrimination and residential segregation, which have been pervasive throughout the development of Charlanta.

A survey-based assessment of perceived flood risk in urban areas of the United States Publication date: December 2019 Source: Anthropocene, Volume 28 Author(s): Sharon L. Harlan, Mariana J. Sarango, Elizabeth A. Mack, Timothy A. Stephens Abstract How people perceive the risks of climatic hazards is currently a major research thrust in the field of risk perception. In the wake of recent flood disasters in the United States (US) and globally, more researchers are investigating social vulnerabilities as well as the role of cognition in explaining risk perceptions. This study analyzed how people in the US perceive the risk (i.e., likelihood and seriousness) of flooding via a layered analysis that considered several plausible and intertwined lines of inquiry from the risk perception literature. We surveyed 9250 individuals within nine major urban areas, including the largest city and one smaller city in each region. The National Flood Hazard Layer product provided data for deriving their potential exposure to flood hazards. The analyses tested and confirmed several hypotheses drawn from Social Vulnerability Theory and from Protective Motivation Theory: characteristics associated with social vulnerability (older, female, race/ethnic minorities, low income), previous experiences with and awareness of flood news, and potential exposure to flood hazard (local fraction of flood prone area) significantly increased risk perceptions of floods. Self-confidence in ability to cope with a future flood disaster lowered risk perceptions. This study is the first snapshot of flood risk perceptions nationwide in the US. It points to needs for more theoretically-driven research about flood risk perceptions and behaviors, flood risk communication within local communities, and more social and economic support for vulnerable populations.

Integrating evidence of land use and land cover change for land management policy formulation along the Kenya-Tanzania borderlands Publication date: December 2019 Source: Anthropocene, Volume 28 Author(s): Colin J. Courtney Mustaphi, Claudia Capitani, Oliver Boles, Rebecca Kariuki, Rebecca Newman, Linus Munishi, Rob Marchant, Paul Lane Abstract This paper presents an overview of the scientific evidence providing insights into long term ecosystem and social dynamics across the northern Tanzania and southern Kenya borderlands. The data sources covered a range from palaeoenvironmental records and archaeological information to remote sensing and social science studies that examined human-environmental interactions and land use land cover changes (LULCC) in the region. This knowledge map of published LULCC research contributes to current debates about the drivers and dynamics of LULCC. The review aims to facilitate both multidisciplinary LULCC research and evidence-based policy analyses to improve familiarity and engagement between LULCC knowledge producers and end-users and to motivate research integration for land management policy formulation. Improving familiarity among researchers and non-academic stakeholders through the collation and synthesis of the scientific literature is among the challenges hindering policy formulation and land management decision-making by various stakeholders along the Kenya-Tanzania borderlands. Knowledge syntheses are necessary; yet, do not fully bridge the gap between knowledge and policy action. Cooperation across the science-policy interface is fundamental for the co-production of research questions by academics, policy makers and diverse stakeholders aimed at supporting land management decision making. For improved co-development and co-benefitting outcomes, the LULCC scientific community needs to mobilise knowledge for a broader audience and to advance co-development of relevant and meaningful LULCC products.

Impacts of distinct spatial arrangements of impervious surfaces on runoff and sediment fluxes from laboratory experiments Publication date: December 2019 Source: Anthropocene, Volume 28 Author(s): C.S.S. Ferreira, R. Moruzzi, J.M.G.P. Isidoro, M. Tudor, M. Vargas, A.J.D. Ferreira, J.L.M.P. de Lima Abstract Urbanization affects runoff processes and sediment transport, but the magnitude of the impacts remains poorly understood. Different spatial patterns of pervious and impervious surfaces influence flow and sediment connectivity between hillslopes and stream networks. Following years of research on the peri-urbanizing Ribeira dos Covões catchment in Portugal, this study uses laboratory rainfall simulation experiments to better assess the impact of  soil and pavement patterns on runoff (amount, runoff start and stop times) and sediment transport. Based on urban cores observed in the study catchment, the investigation focused on seven spatial patterns: bare soil (S), 100% pavement (P), and 60% pavement under continuous - C - surface placed upslope (CU) and downslope (CD), and dispersed - D - over the surface with regular (DR), irregular (DI) and linear (DL) distribution. A 1.00 m × 1.00 m flume, 0.05 m deep with a 9° slope, facilitated the experiments. The study used sandy-loam soil (1500 kg m−3) with concrete slabs representing pavement. Each experiment comprised a series of four rainfall simulations, each lasting 20 min (50 mm h−1), separated by 30-min intervals, to assess the impact of different initial soil moisture conditions. Results indicate that both spatial pattern and soil moisture drive runoff. Under dry conditions, CD provides runoff that is 7 times faster and about 4% higher than that for CU. Already wet conditions, however, produced 12% more runoff on CU than on CD. The greater runoff arose from faster soil saturation, driven by soil moisture increasing more quickly during the rainfall, as well as upstream runoff from paved surfaces, though runoff took longer to reach the outlet. The dispersed pavement pattern only affected runoff amount, with DL producing the highest coefficients (40–71%) and DI the lowest (25–55%), since longer flow paths increase the opportunities for water infiltration.  Additionally, CU yielded 40% more sediment transport  than CD, but the three dispersed patterns did not show a significant impact (p > 0.05). The results suggest that appropriate planning can reduce flood hazard and land degradation in urban areas, in particular by using dispersed patterns of sealed surfaces to enhance water infiltration and retention. Graphical abstract Urban planning should favour water infiltration and retention, by using irregular dispersed patterns.

Greenhouse gas flux from stormwater ponds in southeastern Virginia (USA) Publication date: December 2019 Source: Anthropocene, Volume 28 Author(s): A.L. Gorsky, G.A. Racanelli, A.C. Belvin, R.M. Chambers Abstract Stormwater ponds are ubiquitous features of developed landscapes of the eastern United States. Their design specifically controls the pace of water runoff from impervious cover of surrounding watersheds. Ponds accumulate organic matter that typically decomposes anaerobically in bottom sediments, and thus may be significant sources of greenhouse gases to the atmosphere (e.g., carbon dioxide (CO2), methane (CH4)). We sampled fifteen stormwater retention ponds in southeastern Virginia (USA) during summer 2018 to determine the diffusive emission of greenhouse gases with respect to measured environmental parameters. The equivalent CO2 (CO2e) flux from ponds ranged from 8.3 to 80 mmol m-2 h-1, with CH4 contributing 94%, CO2 6% and nitrous oxide less than 1% of the CO2e flux, on average. From linear mixed-effects modelling, diffusive flux of CO2 was inversely associated with pH. Maximum depth best explained diffusive flux of CH4, with surface area of secondary importance, i.e. CH4 flux was higher in smaller and more shallow ponds. With 300 stormwater ponds in the county where we conducted this study, we estimate that, during a 100-day warm season, these ponds emit 2.3 × 109 ± 1.5 × 109 SD g C as CO2e. As small, human-constructed ponds are becoming common features of urbanizing landscapes globally, results from this study suggest that, collectively, small ponds can contribute substantially to climate forcing. Better pond designs that reduce sediment methanogenesis, however, can mitigate the hypothesized potential disservice of GHG emissions from unvegetated stormwater retention ponds.

The geological significance of novel anthropogenic materials: Deposits of industrial waste and by-products Publication date: December 2019 Source: Anthropocene, Volume 28 Author(s): Joris J. Dijkstra, Rob N.J. Comans, Jeroen Schokker, Michiel J. van der Meulen Abstract Industrial wastes and by-products are increasingly (re-)used as filling material in constructions. To enhance awareness among the geological community of the growing and widespread occurrence of deposits that contain these “novel anthropogenic materials”, this paper reviews three volumetrically important materials: (1) ash remaining from the incineration of household waste (Municipal Solid Waste Incineration bottom ash), (2) slag from steel production, and (3) the stony aggregate fraction of construction and demolition waste. We review their origin, main geochemical weathering reactions, and influence on the natural geogenic environment. These materials have properties that set them apart from the geogenic materials that they replace and overlie. They are formed under high-temperature conditions, are thermodynamically unstable, and may exhibit physical and chemical changes on relatively short timescales, an aspect relatively new for mapping geologists. Because knowledge of deposits in the shallow urban subsurface is increasingly important for urban planning, more articulation and detail in the classification of novel anthropogenic materials is necessary.

Oceanic mercury concentrations on both sides of the Strait of Gibraltar decreased between 1989 and 2012 Publication date: Available online 29 November 2019 Source: Anthropocene Author(s): Daniel Cossa, Joël Knoery, Marie Boye, Nicolas Marusczak, Bastien Thomas, Philippe Courau, Francesca Sprovieri Abstract Mercury (Hg) is a toxic metal that threatens the health of aquatic ecosystems and fish consumers. Its natural cycle has been deeply perturbed by Anthropogenic Hg emissions have deeply perturbed its natural cycle, especially since the start of the Industrial Revolution circa 1850 CE. Anthropogenic Hg emissions from North America and Europe have decreased by a factor of two in the last decades following the implementation of strict regulations. The response of North Atlantic Ocean and Mediterranean waters to this decrease remains poorly documented by field observations. A comparison of results obtained between 1989 and 2012 shows a significant decrease of Hg concentrations in waters on both sides of the Strait of Gibraltar. West of Gibraltar, the Hg decrease ranges from ∼35 % in the upper North East Atlantic Deep Water to ∼50 % in the North East Atlantic Central Water. East of Gibraltar, the observed decrease is ∼30 % in the Western Mediterranean Deep Water. No decrease is observed in the deep Atlantic Ocean layer that formed before the industrial era. These results strongly substantiate the effectiveness of global anti-pollution policies on Hg contamination in oceanic waters. A consequent decline of Hg bioaccumulation in Northeastern Atlantic and Western Mediterranean pelagic ecosystems still requires verification. Graphical abstract

Probabilistic mapping of flood hazards: depicting uncertainty in streamflow, land use, and geomorphic adjustment Publication date: Available online 29 November 2019 Source: Anthropocene Author(s): Timothy A. Stephens, Brian P. Bledsoe Abstract Spatial and temporal variability in precipitation, land use, and river channels introduce uncertainty in flood estimates and pose challenges for floodplain management and mitigation. Yet, standard deterministic methods for quantifying flood hazards and evaluating risk assume stationarity in a nonstationary world and fail to account for uncertainties as they translate to flood hazards. A need exists for improved methods to portray flood hazards that incorporate uncertainty and enable integrated water management. This paper presents novel techniques for evaluating flood hazards through probabilistic flood inundation maps that reflect uncertainty quantified through Monte-Carlo analyses of model inputs and parameters. These techniques represent a first in simultaneously varying discharge, friction parameters, and channel change in probabilistic floodplain mapping while maintaining the high level of detail implemented in regulatory hydraulic models. This study evaluated four methods for quantifying the 1% annual exceedance probability flood, including a nonstationary approach, at an urban watershed in Charlotte, North Carolina, USA. The range of variability in flood extents resulting from Monte-Carlo simulations was spatially variable, and the likelihood of inundation revealed areas of elevated or hidden risk that were not revealed by deterministic regulatory flood hazard boundaries. The nonstationary approach indicates a significant increase in flood hazards and suggests that the regulatory floodplain boundary underestimates and miscommunicates its intended risk status. A simplified approach for estimating uncertainty in flood hazards closely matched ensemble results, providing managers a practical method for conducting uncertainty analysis. These techniques can aid floodplain management by accounting for the inherent uncertainty in model estimates and the potential nonstationary behavior of flood hazards.