scholarly journals Quantitative analysis of the impacts of climate and land-cover changes on urban flood runoffs: a case of Dar es Salaam, Tanzania

2021 ◽  
Author(s):  
Philip Mzava ◽  
Patrick Valimba ◽  
Joel Nobert
Keyword(s):  
Climate Change ◽  
Land Cover ◽  
Land Cover Change ◽  
Dar Es Salaam ◽  
Land Cover Changes ◽  
Urban Flooding ◽  
Combined Effects ◽  
Peak Flows ◽  
The Past ◽  
The Future

Abstract Over the past half-century, the risk of urban flooding in Dar es Salaam has increased due to changes in land cover coupled with climatic changes. This paper aimed to quantify the impacts of climate and land-cover changes on the magnitudes and frequencies of flood runoffs in urban Dar es Salaam, Tanzania. A calibrated and validated SWAT rainfall-runoff model was used to generate flood hydrographs for the period 1969–2050 using historical rainfall data and projected rainfall based on the CORDEX-Africa regional climate model. Results showed that climate change has a greater impact on change in peak flows than land-cover change when the two are treated separately in theory. It was observed that, in the past, the probability of occurrence of urban flooding in the study area was likely to be increased up to 1.5-fold by climate change relative to land-cover change. In the future, this figure is estimated to decrease to 1.1-fold. The coupled effects of climate and land-cover changes cause a much bigger impact on change in peak flows than any separate scenario; this scenario represents the actual scenario on the ground. From the combined effects of climate and land-cover changes, the magnitudes of mean peak flows were determined to increase between 34.4 and 58.6% in the future relative to the past. However, the change in peak flows from combined effects of climate and land-cover changes will decrease by 36.3% in the future relative to the past; owing to the lesser variations in climate and land-cover changes in the future compared with those of the past.

scholarly journals Impact of future land cover changes on HNO<sub>3</sub> and O<sub>3</sub> surface dry deposition

2015 ◽  
Vol 15 (13) ◽  
pp. 18459-18485
Author(s):  
T. Verbeke ◽  
J. Lathière ◽  
S. Szopa ◽  
N. de Noblet-Ducoudré
Keyword(s):  
Climate Change ◽  
Land Cover ◽  
Land Cover Change ◽  
Dry Deposition ◽  
Chemical Properties ◽  
Land Cover Changes ◽  
Vegetation Distribution ◽  
The Future ◽  
Change Impact ◽  
The Impact

Abstract. Dry deposition is a key component of surface–atmosphere exchange of compounds, acting as a sink for several chemical species. Meteorological factors, chemical properties of the trace gas considered and land surface properties are strong drivers of dry deposition efficiency and variability. Under both climatic and anthropogenic pressure, the vegetation distribution over the Earth has been changing a lot over the past centuries, and could be significantly altered in the future. In this study, we perform a modeling investigation of the potential impact of land-cover changes between present-day (2006) and the future (2050) on dry deposition rates, with special interest for ozone (O3) and nitric acid vapor (HNO3), two compounds which are characterized by very different physico-chemical properties. The 3-D chemistry transport model LMDz-INCA is used, considering changes in vegetation distribution based on the three future projections RCPs 2.6, 4.5 and 8.5. The 2050 RCP 8.5 vegetation distribution leads to a rise up to 7 % (+0.02 cm s−1) in VdO3 and a decrease of −0.06 cm s−1 in VdHNO3 relative to the present day values in tropical Africa, and up to +18 and −15 % respectively in Australia. When taking into account the RCP 4.5 scenario, which shows dramatic land cover change in Eurasia, VdHNO3 increases by up to 20 % (annual-mean value) and reduces VdO3 by the same magnitude in this region. When analyzing the impact of dry deposition change on atmospheric chemical composition, our model calculates that the effect is lower than 1 ppb on annual mean surface ozone concentration, for both for the RCP8.5 and RCP2.6 scenarios. The impact on HNO3 surface concentrations is more disparate between the two scenarios, regarding the spatial repartition of effects. In the case of the RCP 4.5 scenario, a significant increase of the surface O3 concentration reaching locally up to 5 ppb (+5 %) is calculated on average during the June–August period. This scenario induces also an increase of HNO3 deposited flux exceeding locally 10 % for monthly values. Comparing the impact of land-cover change to the impact of climate change, considering a 0.93 °C increase of global temperature, on dry deposition velocities, we estimate that the strongest increase over lands occurs in the North Hemisphere during winter especially in Eurasia, by +50 % (+0.07 cm s−1) for VdO3 and +100 % (+0.9 cm s−1) for VdHNO3. However, different regions are affected by both changes, with climate change impact on deposition characterized by a latitudinal gradient, while the land-cover change impact is much more heterogeneous depending on vegetation distribution modification described in the future RCP scenarios. The impact of long-term land-cover changes on dry deposition is shown to be non-negligible and should be therefore considered in biosphere-atmospheric chemistry interaction studies in order to have a fully consistent picture.

scholarly journals Impacts of historical climate and land cover changes on tropospheric ozone air quality and public health in East Asia over 1980–2010

2015 ◽  
Vol 15 (10) ◽  
pp. 14111-14139 ◽  
Author(s):  
Y. Fu ◽  
A. P. K. Tai
Keyword(s):  
Public Health ◽  
Climate Change ◽  
Air Quality ◽  
Land Cover ◽  
East Asia ◽  
Land Cover Change ◽  
Surface Ozone ◽  
Land Cover Changes ◽  
The Past ◽  
Premature Deaths

Abstract. Understanding how historical climate and land cover changes have affected tropospheric ozone in East Asia would help constrain the large uncertainties associated with future East Asian air quality projections. We perform a series of simulations using a global chemical transport model driven by assimilated meteorological data and a suite of land cover and land use data to examine the public health effects associated with changes in climate, land cover, land use, and anthropogenic emissions over the past 30 years (1980–2010) in East Asia. We find that over 1980–2010 land cover change alone could lead to a decrease in summertime surface ozone by up to 4 ppbv in East Asia and ~2000 fewer ozone-related premature deaths per year, driven mostly by enhanced dry deposition resulting from climate- and CO2-induced increase in vegetation density, which more than offsets the effect of reduced isoprene emission arising from cropland expansion. Over the same period, climate change alone could lead to an increase in summertime ozone by 2–10 ppbv in most regions of East Asia and ~6000 more premature deaths annually, mostly attributable to warming. The combined impacts (−2 to +12 ppbv) show that while the effect of climate change is more pronounced, land cover change could offset part of the climate effect and lead to a previously unknown public health benefit. While the changes in anthropogenic emissions remain the largest contributor to deteriorating ozone air quality in East Asia over the past 30 years, we show that climate change and land cover changes could lead to a substantial modification of ozone levels, and thus should come into consideration when formulating future air quality management strategies. We also show that the sensitivity of surface ozone to land cover change is more dependent on dry deposition than isoprene emission in most of East Asia, leading to ozone responses that are quite distinct from that in North America, where most ozone-vegetation sensitivity studies to date have been conducted.

scholarly journals Climate or land cover variations: what is driving observed changes in river peak flows? A data-based attribution study

2019 ◽  
Vol 23 (2) ◽  
pp. 871-882 ◽  
Author(s):  
Jan De Niel ◽  
Patrick Willems
Keyword(s):  
Climate Change ◽  
Land Cover ◽  
Peak Flow ◽  
Hydrological Cycle ◽  
Interaction Effects ◽  
Land Cover Changes ◽  
Climate Variations ◽  
Peak Flows ◽  
Catchment Characteristics ◽  
Flows Over Time

Abstract. Climate change and land cover changes are influencing the hydrological regime of rivers worldwide. In Flanders (Belgium), the intensification of the hydrological cycle caused by climate change is projected to cause more flooding in winters, and land use and land cover changes could amplify these effects by, for example, making runoff on paved surfaces faster. The relative importance of both drivers, however, is still uncertain, and interaction effects between both drivers are not yet well understood. In order to better understand the hydrological impact of climate variations and land cover changes, including their interaction effects, we fitted a statistical model for historical data over 3 decades for 29 catchments in Flanders. The model is able to explain 60 % of the changes in river peak flows over time. It was found that catchment characteristics explain up to 18 % of changes in river peak flows, 6 % of changes in climate variability and 8 % of land cover changes. Steep catchments and catchments with a high proportion of loamic soils are subject to higher peak flows, and an increase in urban area of 1 % might cause increases in river peak flows up to 5 %. Interactions between catchment characteristics, climate variations and land cover changes explain up to 32 % of the peak-flow changes, where flat catchments with a low loamic soil content are more sensitive to land cover changes with respect to peak-flow anomalies. This shows the importance of including such interaction terms in data-based attribution studies.

scholarly journals Climate or land cover variations: what is driving observed changes in river peak flows? A data-based attribution study

2018 ◽  
Author(s):  
Jan De Niel ◽  
Patrick Willems
Keyword(s):  
Climate Change ◽  
Land Cover ◽  
Climate Variability ◽  
Hydrological Cycle ◽  
Hydrological Regime ◽  
Interaction Effects ◽  
Land Cover Changes ◽  
Peak Flows ◽  
Catchment Characteristics ◽  
Interaction Terms

Abstract. Climate change and land cover changes are influencing the hydrological regime of our rivers. The intensification of the hydrological cycle caused by climate change is projected to cause more flooding in winters and an increased urbanization could amplify these effects by a quicker runoff on paved surfaces. The relative importance of both drivers, however, is still uncertain and interaction effects between both drivers are not yet well understood. In order to better understand the hydrological impact of climate variability and land cover changes, including their interaction effects, we fitted a statistical model to historical data over 3 decades for 29 catchments in Flanders, covering various catchment characteristics. It was found that the catchment characteristics explain up to 18 % of changes in river peak flows, climate variability 6 % and land cover changes 8 %. Interaction terms explain up to 32 %. An increase in urban area of +1 % might cause increases in river peak flows up to +5 %.

scholarly journals Impact of future land-cover changes on HNO<sub>3</sub> and O<sub>3</sub> surface dry deposition

2015 ◽  
Vol 15 (23) ◽  
pp. 13555-13568 ◽  
Author(s):  
T. Verbeke ◽  
J. Lathière ◽  
S. Szopa ◽  
N. de Noblet-Ducoudré
Keyword(s):  
Land Cover ◽  
Land Cover Change ◽  
Dry Deposition ◽  
Deposition Velocity ◽  
Land Cover Changes ◽  
Vegetation Distribution ◽  
Deposition Velocities ◽  
The Future ◽  
Rcp 8.5 ◽  
The Impact

Abstract. Dry deposition is a key component of surface–atmosphere exchange of compounds, acting as a sink for several chemical species. Meteorological factors, chemical properties of the trace gas considered and land surface properties are strong drivers of dry deposition efficiency and variability. Under both climatic and anthropogenic pressure, the vegetation distribution over the Earth has been changing a lot over the past centuries and could be significantly altered in the future. In this study, we perform a modeling investigation of the potential impact of land-cover changes between the present day (2006) and the future (2050) on dry deposition velocities at the surface, with special interest for ozone (O3) and nitric acid (HNO3), two compounds which are characterized by very different physicochemical properties. The 3-D chemistry-transport model LMDz-INCA is used, considering changes in vegetation distribution based on the three future projections, RCPs 2.6, 4.5 and 8.5, and present-day (2007) meteorology. The 2050 RCP 8.5 vegetation distribution leads to a rise of up to 7 % (+0.02 cm s−1) in the surface deposition velocity calculated for ozone (Vd,O3) and a decrease of −0.06 cm s−1 in the surface deposition velocity calculated for nitric acid (Vd,HNO3) relative to the present-day values in tropical Africa and up to +18 and −15 %, respectively, in Australia. When taking into account the RCP 4.5 scenario, which shows dramatic land-cover change in Eurasia, Vd,HNO3 increases by up to 20 % (annual-mean value) and reduces Vd,O3 by the same magnitude in this region. When analyzing the impact of surface dry deposition change on atmospheric chemical composition, our model calculates that the effect is lower than 1 ppb on annual-mean surface ozone concentration for both the RCP 8.5 and RCP 2.6 scenarios. The impact on HNO3 surface concentrations is more disparate between the two scenarios regarding the spatial repartition of effects. In the case of the RCP 4.5 scenario, a significant increase of the surface O3 concentration reaching locally by up to 5 ppb (+5 %) is calculated on average during the June–August period. This scenario also induces an increase of HNO3 deposited flux exceeding locally 10 % for monthly values. Comparing the impact of land-cover change to the impact of climate change, considering a 0.93 °C increase of global temperature, on dry deposition velocities, we estimate that the strongest increase over lands occurs in the Northern Hemisphere during winter, especially in Eurasia, by +50 % (+0.07 cm s−1) for Vd,O3 and +100 % (+0.9 cm s−1) for Vd,HNO3. However, different regions are affected by both changes, with climate change impact on deposition characterized by a latitudinal gradient, while the land-cover change impact is much more heterogeneous depending on vegetation distribution modification described in the future RCP scenarios. The impact of long-term land-cover changes on dry deposition is shown to be significant and to differ strongly from one scenario to another. It should therefore be considered in biosphere–atmospheric chemistry interaction studies in order to have a fully consistent picture.

scholarly journals Land-Cover Change and the Future of the Apennine Brown Bear: A Perspective from the Past

2008 ◽  
Vol 89 (6) ◽  
pp. 1502-1511 ◽  
Author(s):  
Alessandra Falcucci ◽  
Luigi Maiorano ◽  
Paolo Ciucci ◽  
Edward O. Garton ◽  
Luigi Boitani
Keyword(s):  
Land Cover ◽  
Land Cover Change ◽  
Brown Bear ◽  
The Past ◽  
The Future ◽  
Apennine Brown Bear

scholarly journals Extended Dependence of the Hydrological Regime on the Land Cover Change in the Three-North Region of China: An Evaluation under Future Climate Conditions

2019 ◽  
Vol 11 (1) ◽  
pp. 81 ◽  
Author(s):  
Yi Yao ◽  
Xianhong Xie ◽  
Shanshan Meng ◽  
Bowen Zhu ◽  
Kang Zhang ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Cover ◽  
Ecological Restoration ◽  
Regional Scale ◽  
Hydrological Regime ◽  
Future Climate ◽  
Climate Conditions ◽  
The Past ◽  
The Future ◽  
Hydrological Effects

The hydrological regime in arid and semi-arid regions is quite sensitive to climate and land cover changes (LCC). The Three-North region (TNR) in China experiences diverse climate conditions, from arid to humid zones. In this region, substantial LCC has occurred over the past decades due to ecological restoration programs and urban expansion. At a regional scale, the hydrological effects of LCC have been demonstrated to be less observable than the effects of climate change, but it is unclear whether or not the effects of LCC may be intensified by future climate conditions. In this study, we employed remote sensing datasets and a macro-scale hydrological modeling to identify the dependence of the future hydrological regime of the TNR on past LCC. The hydrological effects over the period from 2020–2099 were evaluated based on a Representative Concentration Pathway climate scenario. The results indicated that the forest area increased in the northwest (11,691 km2) and the north (69 km2) of China but declined in the northeast (30,042 km2) over the past three decades. Moreover, the urban area has expanded by 1.3% in the TNR. Under the future climate condition, the hydrological regime will be influenced significantly by LCC. Those changes from 1986 to 2015 may alter the future hydrological cycle mainly by promoting runoff (3.24 mm/year) and decreasing evapotranspiration (3.23 mm/year) over the whole region. The spatial distribution of the effects may be extremely uneven: the effects in humid areas would be stronger than those in other areas. Besides, with rising temperatures and precipitation from 2020 to 2099, the LCC may heighten the risk of dryland expansion and flooding more than climate change alone. Despite uncertainties in the datasets and methods, the regional-scale hydrological model provides new insights into the extended impacts of ecological restoration and urbanization on the hydrological regime of the TNR.

scholarly journals Impacts of land cover change on climate trend in Padang Indonesia

2014 ◽  
Vol 46 (2) ◽  
pp. 138 ◽  
Author(s):  
Dedi Hermon
Keyword(s):  
Climate Change ◽  
Land Cover ◽  
Land Cover Change ◽  
Extreme Temperature ◽  
Extreme Rainfall ◽  
Land Cover Changes ◽  
Forest Land ◽  
Climate Trend ◽  
Extreme Climatic Events ◽  
Expert Team

ἀe purpose of this study was to analyze the trend of climate change through changes in the elements of Green House Gases (GHGs),   includes the trend of CO2, N2O, and CH4. ἀe change of the  extreme rainfall and temperature  indices due to land cover change into developed area in Padang. IdentiḀcation and analysis trends of climate change and extreme climatic events were analyzed by using RclimDex the Expert Team for Climate Change Detection and Indices (ETCCDMI) technique. Where as the analysis and interpretation of  land cover changes  into developed area used Landsat TM 5 and Landsat 1985 7 ETM +  of 2011 by ERDAS 9.2 GIS with the supervised classiḀcation method and GIS Matrix. ἀe results of the study provide informations of land cover changes into developed area at forest land  (11,758.9 ha), shrub (3,337.3 ha), rice Ḁelds (5,977.1 ha), and garden (5,872.4 ha). It has an implication on increasing of  the ele-ments of GHGs concentration such as CO2 (14,1 ppm), N2O (5,4 ppb) and CH4 (24,8 ppb). ἀis condition lead to an extreme temperature and presipitation indexs trends in Padang.

scholarly journals Changes in the Land Surface Energy Budget in Eastern China over the Past Three Decades: Contributions of Land-Cover Change and Climate Change

2014 ◽  
Vol 27 (24) ◽  
pp. 9233-9252 ◽  
Author(s):  
J. W. Yan ◽  
J. Y. Liu ◽  
B. Z. Chen ◽  
M. Feng ◽  
S. F. Fang ◽  
...  
Keyword(s):  
Climate Change ◽  
Heat Flux ◽  
Surface Energy ◽  
Land Cover ◽  
Land Cover Change ◽  
Land Surface ◽  
Energy Exchange ◽  
Eastern China ◽  
Incident Solar Radiation ◽  
The Past

Abstract Sensible heat flux (H), latent heat flux (LE), and net radiation (NR) are important surface energy components that directly influence climate systems. In this study, the changes in the surface energy and their contributions from global climate change and/or land-cover change over eastern China during the past nearly 30 years were investigated and assessed using a process-based land surface model [the Ecosystem–Atmosphere Simulation Scheme (EASS)]. The modeled results show that climate change contributed more to the changes of land surface energy fluxes than land-cover change, with their contribution ratio reaching 4:1 or even higher. Annual average temperature increased before 2000 and reversed thereafter; annual total precipitation continually decreased, and incident solar radiation continually increased over the past nearly 30 years. These climatic changes could lead to increased NR, H, and LE, assuming land cover remained unchanged during the past nearly 30 years. Among these meteorological variables, at spatial distribution, the incident solar radiation has the greatest effect on land surface energy exchange. The impacts of land-cover change on the seasonal variations in land surface heat fluxes between the four periods were large, especially for H. The changes in the regional energy fluxes resulting from different land-cover type conversions varied greatly. The conversion from farmland to evergreen coniferous forests had the greatest influence on land surface energy exchange, leading to a decrease in H by 19.39% and an increase in LE and NR by 7.44% and 2.74%, respectively. The results of this study can provide a basis and reference for climate change adaptation.

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