Impact of draining hilly lands on runoff and on‐site erosion: a case study from humid Ethiopia

The use of drainage ditches on farmland has an impact on erosion processes both on‐site and off‐site, though their environmental impacts are not unequivocal. Here we study the runoff response and related rill erosion after installing drainage ditches and assess the effects of stone bunds in north Ethiopia. Three different land management systems were studied in 10 cropland catchments around Wanzaye during the rainy season of 2013: (1) the exclusive use of drainage ditches (locally called feses), (2) the exclusive use of stone bunds, and (3) a mixture of both systems. Stone bunds are an effective soil and water conservation technique, making the land more resistant against on‐site erosion, and allowing feses to be installed at a larger angle with the contour. The mean rill volumes for the 10 studied cropland catchments during the rainy season of 2013 was 3.73 ± 4.20 m³ ha^?1 corresponding to a soil loss of 5.72 ± 6.30 ton ha^?1. The establishment of feses causes larger rill volumes (R = 0.59, N = 10), although feses are perceived as the best way to avoid soil erosion when no stone bunds are present. The use of feses increases event‐based runoff coefficients (RCs) on cropland from c. 5% to values up to 39%. Also, a combination of low stone bund density and high feses density results in a higher RC, whereas catchments with a high stone bund density and low feses density have a lower RC. Peak runoff discharges decrease when stone bund density increases, whereas feses density is positively related to the peak runoff discharge. A multiple linear relation in which both feses and stone bund densities are used as explanatory variable, performs best in explaining runoff hydrograph peakedness (R² = 83%). Copyright © 2015 John Wiley & Sons, Ltd.     

Using Long-Term Census Data to Inform Restoration Methods for Coastal Dune Vegetation

Barrier islands are exposed to the wind and wave action from storms, which often disturbs both the geomorphology and vegetation. Conservation and restoration efforts for these important habitats could be improved with knowledge of how native plants respond to storms. We analyzed 10 years of annual data of vegetation of St. George Island, Florida, in the Gulf of Mexico, to quantify how the plant community responds to major storms and to predict which dune species might be appropriate for restoration after storm damage across dune zones. This prediction was tested with six plant species that differed in their storm response—from highly negative (local extinction in response to storms) to highly positive (increased abundance in response to storms). We measured transplant survival and growth (plant height and number of shoots) over 2 years in a restoration experiment across three major dune zones. We found that different species can be useful for restoration purposes in different dune zones, depending on both short- and longer-term management strategies. Uniola paniculata is a particularly strong restoration candidate across all dune zones, whereas Muhlenbergia capillaris and Schizachyrium maritimum would be beneficial for restoration in the interdune area. Fimbristylis spp. and Sporobolus virginicus demonstrate the strongest potential for restoration in the interdune and backdune areas. Restoration of disturbed areas often involves the seeding or transplanting of species to stabilize the landscape and initiate the return of the original vegetation. We show that the performance of native species, in response to storms, especially in conjunction with information on plant life history, can be useful for identifying the best species to use for restoration.     

Separating contributions from natural and anthropogenic sources in atmospheric methane from the Black Sea region,Romania

The Danube Delta-Black Sea region of Romania is an important wetland, and this preliminary study evaluates the significance of this region as a source of atmospheric CH₄. Measurements of the mixing ratio and δ¹³C in CH₄ are reported from air and water samples collected at eight sites in the Danube Delta. High mixing ratios of CH₄ were found in air (2500–14,000 ppb) and dissolved in water samples (∼1–10 μmol L⁻¹), demonstrating that the Danube Delta is an important natural source of CH₄. The intercepts on Keeling plots of about −62‰ show that the main source of CH₄ in this region is microbial, probably resulting primarily from acetate fermentation. Atmospheric CH₄ and CO data from the NOAA/ESRL (National Oceanic and Atmospheric Administration/Earth System Research Laboratory) were used to make a preliminary estimate of biogenic CH₄ at the Black Sea sampling site at Constanta (BSC). These data were used to calculate ratios of CH₄/CO in air samples, and using an assumed CH₄/CO anthropogenic emissions ratio of 0.6, fossil fuel emissions at BSC were estimated. Biogenic CH₄ emissions were then estimated by a simple mass balance approach. Keeling plots of well-mixed air from the BSC site suggested a stronger wetland source in summer and a stronger fossil fuel source in winter.     

Planning for resettlement: building partnerships for,by, and with Indigenous peoples

Efforts in the United States to plan or implement relocation in response to climate risks have struggled to improve material conditions for participants, to incorporate local knowledge, and to keep communities intact. Mixed methodologies of community geography provide an opportunity for dialogue and knowledge-sharing to collaboratively diagnose the challenges of climate adaptation led by communities. In this article, we advance a participatory practice model for the co-creation of knowledge initiated during a two-day workshop with members from the Biloxi-Chitimacha-Choctaw Tribe from Isle de Jean Charles in Louisiana, Yup’ik people from Newtok Village in Alaska, and researchers from the MIT Resilient Communities Lab. Building on prior scholarship of indigenizing climate change research, this article shares the experience of the workshop to support knowledge exchange and dialogue, with the goal of understanding how to build participatory and non-extractive community-academic partnerships. We reflect on the community values and principles used to guide this workshop to inform more inclusive and co-produced research partnerships, and pedagogies that can improve and assist the self-determination of groups impacted by climate change. Workshop presentations and discussions highlight interconnected themes of resources, systems & structures, regulatory imbalance, and resilience that underpin climate resettlement. We reflect on the narratives presented by members of both Indigenous tribes and NGO partners that illustrate the shortcomings of resettlement planning practices past and present as perpetuating existing inequality. In response to this structured knowledge exchange, we identify potential roles for community-academic partnerships that aim to improve the equity of existing resettlement models. We propose approaches for incorporating traditional knowledge into the pedagogy, discourse, and practice of academic planning programs.

     

Monsoon fluctuations in two 20,000-Yr B.P. Oxygen-isotope/pollen records off southwest India

Two marine pollen diagrams for sediments off the southwest coast of India provide a 20,000-yr history of the nearby continental vegetation, determined by the monsoon climate, within the framework of the isotopic stratigraphy. Two important phases of the evolution of the monsoon climate are a very arid period about 22,000–18,000 yr B.P. and a very humid period culminating at 11,000 yr B.P. The very arid period corresponds to the lowest pollen representation of mangrove vegetation, which is used here as an indirect indicator of monsoonal runoff. This aridity is due to a very weak southwest airflow, a great reduction of summer monsoonal rainfall, and reduced runoff of the western Ghats rivers. The extension of the monsoon over India after the last glacial maximum has been a gradual process following the northward progression of the Intertropical Convergene Zone. The very humid period, corresponding to the highest pollen representation of mangrove vegetation and the heaviest summer rainfall, is a climatic response to the maximum summer insolation of the Northern Hemisphere at 11,000 yr B.P.     

A first classification scheme of flow-bed interaction for clay-laden density currents and soft substrates

Many aquatic environments exhibit soft, muddy substrates, but this important property has largely been ignored in process-based models of Earth-surface flow. Novel laboratory experiments were carried out to shed light on the feedback processes that occur when particulate density currents (turbidity currents) move over a soft mud substrate. These experiments revealed multiple types of flow-bed interaction and large variations in bed deformation and bed erosion, which are interpreted to be related to the interplay between the shear forces of the current and the stabilising forces in the bed. Changes in this force balance were simulated by varying the clay concentrations in the flow and in the bed. Five different interaction types are described, and dimensional and non-dimensional phase diagrams for flow-bed interaction are presented.     

STRATEGIC PLANNING FOR GEOGRAPHY DEPARTMENTS?

Strategic planning is a technique from the commercial world which could assist geography departments in adapting to today's more demanding administrative environments and thereby further the development of the discipline. This paper sets out the fundamentals of planning as a prelude to a generic departmental plan. Key inclusions are explained and certain problems of application are discussed, should departments adopt such an approach.     

Community structure and grazing of the nano-microzooplankton on the continental shelf of the Bay of Biscay

In order to investigate the parameters controlling the heterotrophic protists (nano-microzooplankton) on the continental shelf of the southern Bay of Biscay, plankton communities and their physico-chemical environment were studied 4 times in February, April, June and September–October 2004 at three stations in the euphotic zone in the Bay of Biscay. The abundance and carbon biomass of heterotrophic protists (ciliates, heterotrophic dinoflagellates and nanoflagellates) as well as all the others groups of plankton (picoplankton, nanophytoplankton, diatoms, autotrophic dinoflagellates, metazoan microzooplankton and mesozooplankton), the environmental parameters and the primary and bacteria production were evaluated at each sampling period. Microzooplankton grazing experiments were undertaken at the same time. Ciliates and heterotrophic dinoflagellates accounted for the main major component of nano- and microzooplankton communities in term of biomass. The total carbon biomass of heterotrophic protists was highest in spring and lowest at the end of summer. The development of heterotrophic protists started after a winter microphytoplankton bloom (principally large diatoms), the biomass was lower in June and was low in September (through inappropriate prey). The carbon requirement of microzooplankton ranged from 50 to more than 100% of daily primary, bacterial and nanoflagellate production. The heterotrophic protist community was predominantly constrained by bottom-up control in spring and at the end of summer via food availability and quality.     

Flake Morphology,Fluvial Dynamics,and Debitage Transport Potential

Since archaeological sites are often located in or near fluvial environments, a thorough understanding of corresponding formation processes is a critical component of archaeological research. Within this context, we address the following question: how does flake morphology condition transport potential? Specifically, do flakes behave as the idealized spheres often used to characterize geological materials and if so, how might this process modify a debitage assemblage? To address this important issue, we present the results of a fluvial transport experiment designed to evaluate the relationships between flake size, shape, weight, curvature, and transport potential. We begin with an overview of fluvial mechanics and previous archaeological fluvial transport studies and use these studies to design an experiment intended to fill gaps in our knowledge of the relationships between flake morphology and transport potential. Our experimental results suggest that all things being equal, flake weight is the most important variable in both settling velocity and transport distance, although flake shape conditions transport as well. Finally, our study demonstrates the potential structure of fluvially transported assemblages as lag deposits and suggests that fluvially transported assemblages may retain key behavioral information.     

Robustness and uncertainties of seismic damage estimates at urban scale: a methodological comparison on the example of the city of Oran (Algeria)

The city of Oran is exposed to a significant seismic hazard, as almost all the northern Algeria territory, where numerous casualties and severe damage occurred in the last decades due to several moderate to large earthquakes. A mitigation policy should include the establishment of priorities to reduce the vulnerability of existing buildings based on the knowledge of the actual urban fabrics. The complexity of vulnerability assessment requires a gradual approach from the urban scale to the building scale. The study reported in this paper corresponds to the first step of such an approach, i.e., a preliminary study of the seismic vulnerability and expected damage within an urban district of the city of Oran, based on a non-dedicated data base from a building survey previously performed for other purposes. The main goals of this study are twofold: (1) an assessment of the degree of uncertainty and robustness of such results through a comparison of the results derived from different urban vulnerability methods (GNDT 2; RISK-UE LM1; and VULNERALP 2.0) and (2) an assessment of the actual level of seismic risk in the city of Oran. Cross-method comparisons and correlations highlight a satisfactory agreement between mean damage estimates at the urban scale, despite significant scattering at the single building scale, and uncertainty levels which vary significantly from one method to the other. For a given scenario, the three methods provide damage estimates lying within half an EMS damage degree of one another, with some systematic positive bias for VULNERALP and negative bias for RISK-UE LM1, especially for masonry buildings. The expected mean damage is very important for intensities 9 and 10, with an average damage grade around 3–4 for intensity 9 and 4–5 for intensity 10. The spatial distribution of damage systematically exhibits larger values in the northern, older, commercial area, than in the southern, more recent and more residential area, in relation to the building typology and the existence of several aggravating factors. Some areas of higher vulnerability / damage can be distinguished, which should receive particular attention for retrofitting priorities or urban planning decisions, also taking into account their cultural heritage value.