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• The runoff, sediment load and runoff erosion power decreased significantly. • Compared with runoff, runoff erosion power-sediment relationship is better. • The power function of runoff erosion power and sediment is better than linear. • Erosion in particular geographic locations responds strongly to runoff erosion power. In recent years, the acceleration of urbanization in the Yangtze River Economic Belt (YREB) has brought about problems such as soil erosion, ecosystem degradation and decline in ecological service functions. Therefore, this paper selects the Fujiang River Basin (FRB) in Upper Yangtze River (UYR), and analyzes the relationship between runoff erosion power (REP) and sediment transport (ST) on the basis of analyzing the variation characteristics of hydrological elements. Based on SWAT model, a variety of scenarios are set up to quantitatively analyze the impact of different land use changes on runoff and ST and REP in the basin. The results indicated that: (1) The annual precipitation in FRB from 1960 to 2018 did not change significantly, while the annual runoff, annual ST and annual REP decreased significantly. Compared with runoff and runoff depth, the relationship between sediment transport modulus (STM) and REP is the best, especially the power function between them is better than the linear function. (2) The results of the evaluation indexes of the simulation results of the SWAT model based on the measured runoff and sediment data from 2008 to 2018 are pass and above, that is, the simulation results are considered reliable. (3) Under the five scenarios of conversion of sloping farmland to forest, conversion of dry land to paddy field and conversion of grassland to bushland and forest land, the runoff and ST in the basin decreased but the overall range was small. The simulation results of SWAT model show that the erosion of specific areas in the basin shows the greatest degree of weakening with the decrease of REP. [ABSTRACT FROM AUTHOR]

Summary Surface runoff is the hydrological process at the origin of phenomena such as soil erosion, floods out of rivers, mudflows, debris flows and can generate major damage. This paper presents a method to create maps of surface runoff susceptibility. The method, called IRIP (Indicator of Intense Pluvial Runoff, French acronym), uses a combination of landscape factors to create three maps representing the susceptibility (1) to generate, (2) to transfer, and (3) to accumulate surface runoff. The method input data are the topography, the land use and the soil type. The method aims to be simple to implement and robust for any type of study area, with no requirement for calibration or specific input format. In a second part, the paper focuses on the evaluation of the surface runoff susceptibility maps. The method is applied in the Lézarde catchment (210 km 2 , northern France) and the susceptibility maps are evaluated by comparison with two risk regulatory zonings of surface runoff and soil erosion, and two databases of surface runoff impacts on roads and railways. Comparison tests are performed using a standard verification method for dichotomous forecasting along with five verification indicators: accuracy, bias, success ratio, probability of detection, and false alarm ratio. The evaluation shows that the susceptibility map of surface runoff accumulation is able to identify the concentrated surface runoff flows and that the susceptibility map of transfer is able to identify areas that are susceptible to soil erosion. Concerning the ability of the IRIP method to detect sections of the transportation network susceptible to be impacted by surface runoff, the evaluation tests show promising probabilities of detection (73–90%) but also high false alarm ratios (77–92%). However, a qualitative analysis of the local configuration of the infrastructure shows that taking into account the transportation network vulnerability can explain numerous false alarms. This paper shows that the IRIP method can be a valuable tool to facilitate field analysis and perform surface runoff zonings and opens interesting prospects for the use of the IRIP method in a context of risk management. [ABSTRACT FROM AUTHOR]

Gully width (W) is usually characterized by having a power relation with discharge. However, calculating runoff discharge in ungauged basins, where these gullies typically form, is inherently difficult and associated with large uncertainties. This paper examines a simplified approach to relating gully width directly to the runoff contributing area (A) in a cultivated area in SW Spain. The effect of rainfall and land use on this W-A relation was also analysed. Gully width was measured in 46 sections through the analysis of 10 historical orthophotos between 1956 and 2013, in a 21 km2 catchment in S Spain. These were validated by field measurements in 2013. Widening rates varied strongly over time, at between ~0 and 2,19 m year−1. No significant differences in the gully widening rates were found between the two land uses present in the study zone (olive groves and herbaceous crops). The data obtained show a significant power relation of the form W = αA β for all time periods analysed, except for 1980, when many gullies were filled in artificially due to a change in land use in the study area. The power relation coefficient (β) varied at between 0.2 and 0.3. A good correlation was obtained between the number of days with daily rainfall of above 13 mm and the increase in the α coefficient over time. The results of this study on gully width dynamics provide new insights into improving the estimation of gully volume, for example in combination with gully headcut retreat models, and including the effects of different climate scenarios. • Gully width dynamics were reconstructed from aerial orthophotos in Mediterranean crops. • We found a significant correlation between gully width and runoff contribution area. • Gully widening rates were successfully correlated with a rainfall index based on daily rainfall thresholds. [ABSTRACT FROM AUTHOR]

Abstract: Landscape metrics are used in a wide range of environmental studies such as land use change and land degradation studies, soil erosion and run-off predictions, management of hunting communities, and strategic planning for environmental management, to name just a few. Due to their utility for a variety of applications, there are many indices and software packages that have been designed to provide calculations and analysis of landscape structure patterns in categorical maps. With the purpose of making a comparison between the most used tools (Fragstats, V-Late, PA4…), this paper examines their advantages and disadvantages in order to create a list of common features that need to be incorporated into this type of software. An Application Programming Interface (API) is produced without limitations on data input, that is capable of calculating vector or raster metrics and is extensible. This API should make it possible not only to build third party applications easily, but also make it possible to add new metrics and research into new paradigms related to traditional landscape metrics. Land-metrics DIY (Do It Yourself) is the library presented in this paper. It can calculate almost 40 landscape metrics from geometry provided by an ESRI Shapefile. [Copyright &y& Elsevier]

• Parameter uncertainty varies over time scales due to land use change (LUC). • The calibrated daily runoff model is deficient for the extreme flow changes. • Model structure impacts the extreme runoff direction change for moderate LUC. Hydrological modeling has provided key insights into the mechanisms of land-use change impacts on runoff. However, the uncertainty of this impact is poorly understood. This paper examines the uncertainty originated from hydrological models' parameters and structure in simulating hydrological responses to land use change on daily, monthly and annual time scales. Two hydrological models, SWAT and HSPF, were applied to simulate the runoff response in the Xitiaoxi basin of eastern China. The effects of three land use scenarios (in 1985, 2002 and 2014) were analyzed with respect to the expansion of urban areas and reduction of cropland and forests. The changes in streamflow with multi-timescales between two models were compared at the whole basin and the sub-basin scales. The parameter uncertainty was estimated based on a sequential uncertainty analysis method (SUFI-2). The results indicate that the two models (SWAT and HSPF) could reproduce the observed daily and seasonal flows well, but they cannot accurately reconstruct the extreme flows (such as annual 7-day minimum discharge, R_7dMIN). The effect of parameter uncertainty on streamflow varies over time scales. The simulated annual and monthly runoff change values show large discrepancies but with same trends. The simulated changes for annual maximum discharge (R_1dMAX) and R_7dMIN often show different signs. The average width of the predictive interval in the relative change of different flow characteristics exceeded 100% of the average relative changes for both models. HSPF tends to present larger relative changes for the annual and monthly runoffs compared to SWAT. Moreover, the model choice could affect the direction change in R_1dMAX and R_7dMIN. However, when land use change was significant to a certain degree, both models simulated increased R_1dMAX and decreased R_7dMIN, but with different significance levels. The study suggests that the model structure represents an additional uncertainty, which should be accounted for in the land-use change impact assessment. [ABSTRACT FROM AUTHOR]

Highlights • A sound understanding of climate change is required in support of current flood risk management. • The hydrological behaviour of the Schijn River, Belgium, was studied from urbanization and climate scenarios perspectives. • Peak flows for rural and urban runoff were significantly higher than existing rainfall-runoff model (PDM) flows because of faster and more peaked urban runoff response. • The impact of climate change on current and future conditions was assessed by estimating peak flows with respect to return periods from the flood frequency curve. • Climate change impacts were found to contribute the most in producing peak flows in coming years, while increased urbanization takes the second place for both hourly and daily values. • Results on urbanization effect and climate change impact assessment are useful to the water managers for spatial planning, emergency planning and insurance industry. Abstract Flooding is the most common natural disaster in Europe. Modern flood risk management relies not only infrastructure development but also on governmental and non-governmental actors applying legal, economic and communicative water management instruments. Within the European Union (EU), flood management closely relies on policy set at the EU and national levels. It is now recognized that a sound understanding of climate change is required in addition to current management by taking into account land use change and socio-political context, as climate and land use changes have major impacts on hydrological responses. This paper investigates the hydrological behavior due to urbanization under current and future climate scenarios of high summer and high winter rainfall for 20 sub-catchments of the Schijn River, located in the Flanders region near Antwerp, Belgium. As urbanization increases and existing rainfall-runoff models neglecting the specific behavior of urban runoff, a hydrological model was developed based on a basic reservoir concept and applied to the existing rainfall-runoff model (PDM) flow to examine the specific urban contribution. Results revealed that peak flow for urban runoff and the total peak flow (i.e. rural and urban runoff) were significantly higher (i.e. ranges from 200% to 500%) than the existing rainfall-runoff model (PDM) flows, because of faster and more peaked urban runoff response. The impact of climate change on current and future conditions was also assessed by estimating peak flows with respect to return periods from the flood frequency curve. The predicted peak flow of high summer future climate scenario was significantly higher (i.e. ranges from 200% to 250%) than that of the current climatic condition for this region. Furthermore, hourly peak flow and daily volume ratios of 100-year return period for the highest, lowest and average impervious area were projected for the time horizon of the year 2100. It is concluded that climate change impacts contribute the most in producing peak flow in coming years, while increased urbanization takes the second place for both hourly and daily values. Results on urbanization effect and climate change impact assessment are useful to the water managers for spatial planning, emergency planning and insurance industry. [ABSTRACT FROM AUTHOR]

Abstract: Land use change has significant impacts on hydrologic processes at the watershed level. This paper combines an empirical land use change model and an event-scale, rainfall-runoff model to quantify the impacts of potential land use change on the storm-runoff generation in the Xitiaoxi basin upstream of Taihu Lake watershed. The HEC–HMS rainfall-runoff model is calibrated and validated for 7 storm events in the study area, and the results show good consistency between the simulated and measured hydrographs at the outlet of the basin with Nash–Sutcliff efficiency ranging from 75% to 95%. Then two future land use scenarios for the year 2050 are forecasted using the CLUE-s model based on the land use of 2002: (1) scenario A with an increase in urban area from 9.2% to 17% of the entire watershed and (2) scenario B with an increase from 9.2% to 14%. Finally, the calibrated HEC–HMS model is applied for these future land use scenarios under designed storms with different recurrence intervals to assess the potential land use impacts on the storm-runoff generation. The results indicate that the future land use scenarios are projected to increase the total runoff as well as the peak discharge, and that the magnitude of increment relates to the expansion rate of built-up area. In the case of rainstorms with recurrence intervals of 10, 50 and 100 years, the simulated peak discharges increase by 3.8%, 2.6% and 2.3% under scenario A, and by 2.8%, 1.9% and 1.7% under scenario B, respectively; while the total runoff is projected to increase by 4.7%, 3.4% and 3.0% under scenario A, and by 3.3%, 2.5% and 2.1% under scenario B. It can be concluded that the sensitivity of hydrologic response to land use change tends to increase as the recurrence interval of rainfall events decreases. Additionally, remarkable spatial variations of the land use changes and its impacts can be observed at the subbasin level, and the most sensitive subbasin is closeby the city. The results of this paper can provide useful support for land use planning and management, and the methods applied here have proved a useful tool for land use impact studies. [Copyright &y& Elsevier]

Summary: Abundant information is available on West African drought and its hydrological and environmental impacts. Land-use and climatic changes have greatly modified the conditions of Sudanian and Sahelian hydrology, impacting the regime and discharge of the main rivers. Human pressure on the environment (significant increase in crops and disappearance of natural bushes and landscapes, for example) has led to severe soil crusting and desertification throughout Sahelian regions. Despite recent increases in rainfall, the drought has not ended, resulting in two different hydrological evolutions. In the Sudanian areas, stream flows have been reduced, sometimes as much as twice the rainfall reduction rate. In the Sahelian regions, runoff coefficients have increased to such a degree that discharges are increasing, in spite of the reduced rainfall. The main goal of this paper is to synthesize the recent advances in the Sahelian and Sudano-Sahelian West African hydrology. The other objectives are two fold: First, to discuss the “Sahelian Paradox” (the increase in runoff in most of the Sahel during the drought, at least during the 1968–1995 period, as described in the 1980s) and paradox of groundwater highlighted in the square degree of Niamey (the rise in water table levels in some endorheic areas during the same drought, evidenced in the 1990s), and second, to attempt to define the application of their respective geographical areas. The land-use changes act as a general factor of hydrological evolution of soils and basins, while some spatial factors explain the great variability in the response to environmental evolution, such as endorheism, geological context, latitudinal climate gradient, and local hydrodynamic behaviour of environment. This paper is literature-based, and incorporates current research advances in the field, as well as a prospective focused on resources and socio-economic impacts. [Copyright &y& Elsevier]

The paper attempts to determine the extent to which rainfall trends and land use changes influence the river flow regime and flood response of a predominantly agricultural catchment (210 km2) in southwest England. Temporal changes in daily rainfall totals were analysed over annual, seasonal and monthly timescales but although annual average October rainfalls exhibited a weak rising trend (r=0.3, p>0.05), no long-term patterns were observed. Analysis of daily mean discharge data for the River Camel over the period 1965–2000, using the Gumbel distribution, revealed an increase in the magnitude and frequency of peak flows. Land use changes were examined using Agricultural Census Data for 1969, 1979, 1988, 1997 and 2000. Both the number of stock and the area under cereals increased from 1969 to 1997, but cereal production declined substantially between 1997 and 2000. Spatial response patterns were also examined through a comparison of the flow response of the entire Camel catchment with its more complex land use, with the predominantly pastoral De Lank headwater sub-catchment (22 km2), to ascertain the amount of change due to increased livestock numbers alone. No single factor was found to be responsible for the increases in flood frequency and magnitude in the River Camel. Rather, long-term changes in the response of the Camel system appear to emanate from the cumulative impact of subtle changes in climate, combined with increased farming activity plus urban expansion. The paper highlights the inherent difficulties of attempting to disentangle the precise effects of individual land uses on flood responses at the catchment scale and underlines the need for a holistic approach to the management of floods. By the same token, sustainable catchment management can only be achieved through greater awareness of the potential for complex, small-scale land use decisions to result in large-scale hydrological changes. [Copyright &y& Elsevier]

The global prevalence of rapid and extensive land use change necessitates hydrologic modelling methodologies capable of handling non-stationarity. This is particularly true in the context of Hydrologic Forecasting using Data Assimilation. Data Assimilation has been shown to dramatically improve forecast skill in hydrologic and meteorological applications, although such improvements are conditional on using bias-free observations and model simulations. A hydrologic model calibrated to a particular set of land cover conditions has the potential to produce biased simulations when the catchment is disturbed. This paper sheds new light on the impacts of bias or systematic errors in hydrologic data assimilation, in the context of forecasting in catchments with changing land surface conditions and a model calibrated to pre-change conditions. We posit that in such cases, the impact of systematic model errors on assimilation or forecast quality is dependent on the inherent prediction uncertainty that persists even in pre-change conditions. Through experiments on a range of catchments, we develop a conceptual relationship between total prediction uncertainty and the impacts of land cover changes on the hydrologic regime to demonstrate how forecast quality is affected when using state estimation Data Assimilation with no modifications to account for land cover changes. This work shows that systematic model errors as a result of changing or changed catchment conditions do not always necessitate adjustments to the modelling or assimilation methodology, for instance through re-calibration of the hydrologic model, time varying model parameters or revised offline/online bias estimation. [ABSTRACT FROM AUTHOR]

The Yinjiang River watershed is a typical karst watershed in Southwest China. The present study explored runoff change and its responses to different driving factors in the Yinjiang River watershed over the period of 1984 to 2015. The methods of cumulative anomaly, continuous wavelet analysis, Mann-Kendall rank correlation trend test, and Hurst exponent were applied to analyze the impacts of climate change and human activities on runoff change. The contributions of climate change and human activities to runoff change were quantitatively assessed using the comparative method of the slope changing ratio of cumulative quantity (SCRCQ). The following results were obtained: (1) From 1984 to 2015, runoff and precipitation exhibited no-significant increasing trend, whereas evaporation exhibited significant decreasing trend. (2) In the future, runoff, precipitation, and evaporation will exhibit weak anti-persistent feature with different persistent times. This feature indicated that in their persistent times, runoff and precipitation will continuously decline, whereas evaporation will continuously increase. (3) Runoff and precipitation were well-synchronized with abrupt change features and stage characteristics, and exhibited consistent multi-timescale characteristics that were different from that of evaporation. (4) The contribution of precipitation to runoff change was 50%–60% and was considered high and stable. The contribution of evaporation to runoff change was 10%–90% and was variable with a positive or negative effects. The contribution of human activities to runoff change was 20%–60% and exerted a low positive or negative effect. (5) Climatic factors highly contributed to runoff change. By contrast, the contribution of human activities to runoff change was low. The contribution of climatic factors to runoff change was highly variable because of differences among base periods. In conclusion, this paper provides a basic theoretical understanding of the main factors that contribute to runoff change in a karst watershed. [ABSTRACT FROM AUTHOR]

Universal Soil Loss Equation USLE-based erosion models have been used extensively to complement erosion measurements, to understand the interactions of the different geophysical features into erosion processes and to assess adequate alternative management practices and scenarios analyses. Despite its proved usefulness on different land-uses around the world, there is an urgent need to set up simple tools which do not require an advanced management expertise in terms of both choose of model parameters and calculation ability and which are accurate particularly at the event scale. In this paper the suitability of the Modified USLE (USLE-M) model at the event and the annual scale were evaluated in an olive orchard catchment of 6.1 ha in Spain where a rainfall-runoff-sediment yield dataseries of over 8 years (2005–2013) was available. The model was applied dividing the catchment into morphological units, i.e. areas having a defined aspect, length and steepness. In addition, different model parameterizations of both the crop factor of the Revised USLE factor and β-coefficient of the sediment delivery ratio of each morphological unit were studied in order to describe the seasonal variability of soil conditions along the year. At event scale the best performance of the USLE-M model was obtained using a single value of the β coefficient equal to median value β e,m without considering the seasonal variability of crop factor since it is well-represented by the term rainfall-runoff erosivity index. At the annual scale, the calculation of crop factor values provided a good model performance in estimating sediment yield, with a coefficient of efficiency of 0.96. The analysis demonstrated that the USLE-M model was a useful tool to simulate soil losses at the event and annual scales and its application might provide guidelines for other users. [ABSTRACT FROM AUTHOR]

Runoff from human land-uses is one of the most significant threats to some coastal marine environments. Initiatives to reduce that runoff usually set runoff reduction targets but do not give guidance on how to prioritize the different options that exist to achieve them. This paper demonstrates an easy to interpret economic framework to prioritise investment for conservation projects that aim to reduce pollution of marine ecosystems caused by runoff from agricultural land-uses. We demonstrate how to apply this framework using data on project cost, benefit and feasibility with a subset of projects that have been funded to reduce runoff from subcatchments adjacent to the Great Barrier Reef. Our analysis provides a graphical overview of the cost-effectiveness of the investment options, enables transparent planning for different budgets, assesses the existence of trends in the cost-effectiveness of different categories, and can test if the results are robust under uncertainty in one or more of the parameters. The framework provided solutions that were up to 4 times more efficient than when omitting information on cost or benefit. The presented framework can be used as a benchmark for evaluating results from a range of prioritisation processes against the best possible conservation outcomes. [ABSTRACT FROM AUTHOR]

The changes in runoff and sediment load in the Loess Plateau of China have received considerable attention owing to their dramatic decline during recent decades. In this paper, the impacts of land-use and climate changes on water and sediment yields in the Huangfuchuan River basin (HFCRB) of the Loess Plateau are investigated by combined usage of statistical tests, hydrological modeling, and land-use maps. The temporal trends and abrupt changes in runoff and sediment loads during 1954–2012 are detected by using non-parametric Mann–Kendall and Pettitt tests. The land-use changes between 1980 and 2005 are determined by using transition matrix analysis, and the effects of land-use and climate changes on water and sediment yields are assessed by using the Soil and Water Assessment Tool (SWAT) hydrological model and four scenarios, respectively. The results show significant decreasing trends in both annual runoff and sediment loads, whereas slightly decreasing and significantly increasing trends are detected for annual precipitation and air temperature, respectively. 1984 is identified as the dividing year of the study period. The land-use changes between 1980 and 2005 show significant effects of the Grain for Green Project in China. Both land-use change and climate change have greater impact on the reduction of sediment yield than that of water. Water and sediment yields in the upstream region show more significant decreases than those in the downstream region under different effects. The results obtained in this study can provide useful information for water resource planning and management as well as soil and water conservation in the Loess Plateau region. [ABSTRACT FROM AUTHOR]

The relation between rainfall, runoff, erosion and sediment transport is highly variable in Mediterranean catchments. Their relation can be modified by land use changes and climate oscillations that, ultimately, will control water and sediment yields. This paper analyses rainfall, runoff and sediment transport relations in a meso-scale Mediterranean mountain catchment, the Ribera Salada (NE Iberian Peninsula). A total of 73 floods recorded between November 2005 and November 2008 at the Inglabaga Sediment Transport Station (114.5 km 2 ) have been analysed. Suspended sediment transport and flow discharge were measured continuously. Rainfall data was obtained by means of direct rain gauges and daily rainfall reconstructions from radar information. Results indicate that the annual sediment yield (2.3 t km − 1 y − 1 on average) and the flood-based runoff coefficients (4.1% on average) are low. The Ribera Salada presents a low geomorphological and hydrological activity compared with other Mediterranean mountain catchments. Pearson correlations between rainfall, runoff and sediment transport variables were obtained. The hydrological response of the catchment is controlled by the base flows. The magnitude of suspended sediment concentrations is largely correlated with flood magnitude, while sediment load is correlated with the amount of direct runoff. Multivariate analysis shows that total suspended load can be predicted by integrating rainfall and runoff variables. The total direct runoff is the variable with more weight in the equation. Finally, three main hydro-sedimentary phases within the hydrological year are defined in this catchment: (a) Winter, where the catchment produces only water and very little sediment; (b) Spring, where the majority of water and sediment is produced; and (c) Summer–Autumn, when little runoff is produced but significant amount of sediments is exported out of the catchment. Results show as land use and climate change may have an important role in modifying the cycles of water and sediment yields in Mediterranean mountain catchments. [ABSTRACT FROM AUTHOR]

Summary Modelling hydrology and sediment yield and its scale dependency has been limited by the quantity and quality of instrumental data. This paper aims to apply alternative methods to estimate runoff and sediment production rates at the event-scale and to characterize the hydro-sedimentary response of a highly torrential Mediterranean catchment to historical changes in land use and vegetation. A selection of well-dated and spatially-distributed check dams within the catchment were used to calibrate and validate a hydro-sedimentary distributed model (TETIS). Sediment volumes deposited by individual runoff events and trapped in check dams were estimated on the bases of detailed stratigraphic descriptions and subsequent GPS/TLS surveys. The model results showed a good agreement with the observed water flows and sediment volumes deposited behind several check dams. Management and land uses proved to be a decisive factor in the hydrological behaviour of the catchment, especially affecting erosion and sediment yield. It was observed that while the hydrological response of the catchment was sensitive to the percentage of each land use type, the sedimentary response was more dependent on the spatial distribution of land use. These differences between hydrology and sedimentary behaviour imply that the optimal soil use distribution for soil conservation may differ from the optimal soil use scenario oriented to attenuate flood peaks. This study suggest that soil use policies and erosion mitigation strategies should consider a holistic hydro-sedimentary approach, in order to become an adaptive option to reduce and mitigate the effects of erosion and flood peaks under global change. [ABSTRACT FROM AUTHOR]

The most important anthropogenic influences on climate are the emissions, changes in land use, such as urbanization aural areasnd agriculture. The urban environment has distinctive bioclimatical factors in relation to rural areas. The process of urbanization alters natural surface and atmospheric conditions. Urban areas are characteristic by increased rainwater surface runoff, increased temperatures and decreased evaporation. Exactly evaporation warms the rural surface more than the urban. The paper concerns on the impacts of urbanization that are evaluated by observations in cities with those in rural areas – not so populated and with smaller built areas. We use and asses the difference between trends in monthly average temperatures and trends in monthly precipitations in the cities and the corresponding trends in rural areas. For the trend analysis, the Mann-Kendall nonparametric test is used. Our results show differences in trends in villages and cities. Observed are increased trends in temperature and decreased trends in precipitation due to urban and land-use changes. [ABSTRACT FROM AUTHOR]

This paper describes the results of benchmark testing of land use change impact on direct runoff using Soil Conservation Service-Curve Number (SCS-CN) model in two ungauged neighbouring urban watersheds (Çınar and Kadıyakuplu) in Istanbul, Turkey. To examine this impact, the model was applied to daily rainfall data using three different dated (1982, 1996 and 2012) hydrological soil groups and land use of the two ungauged urban watersheds. Finally, the impact of land use change and model performance were evaluated with the rainfall-runoff regression, the coefficient of determination and the NSE test using benchmark runoff data based on 1982 land use conditions. The results of the analysis indicate that the changing of land use types from natural surfaces to impervious surfaces has a significant impact on surface runoff. Additionally, remarkable spatial variations of the land use changes and their impact on the runoff in 1996 and 2012 were more detected in the Çınar watershed compared with the Kadıyakuplu watershed. The planning decision on land use of the watersheds, has vital role in these differences. The results of this research also reveal that change to intensive land use in urban watersheds has a significantly larger impact on runoff generation than those rainfall. [ABSTRACT FROM AUTHOR]

The quality of water entering the coastal waters of the Great Barrier Reef continues to be of urgent concern for policy makers. Beef grazing and sugarcane cultivation pose special threats at the catchment scale, and past policy approaches and millions in investment have largely proved insufficient to reverse the associated decline in water quality. In this paper, we examine the role of regulation - as one tool of governance - in addressing threats to water quality to the Great Barrier Reef. By adopting a focused study of sugarcane and cattle grazing, and by drawing upon recent developments in regulatory theory, we evaluate the approaches adopted by government, including the recent re-introduction of legislative measures targeting nutrient and sediment loads. Scientific and government consensus appears to be that regulation should form part of a functioning environmental governance system, but it must also be supported by other measures such as economic incentives, education and outreach. Where regulation of land use is required, best practice suggests it should be risk-based, responsive, and cognisant of the regulated industry's attitudinal settings. • Addressing water quality of the Great Barrier Reef requires an effective mix of policy instruments. • Regulatory interventions should support non-regulatory instruments to encourage behavioral change. • Where regulation is adopted, it should be risk-based, responsive, and cognizant of the industry's attitudinal settings. [ABSTRACT FROM AUTHOR]

Abstract: This paper aims to evaluate how varying degrees of land-use/cover (LULC) changes across sub-catchments affect a flood peak at the catchment outlet. The study site was the Konar catchment, a part of the upper Damodar Basin in eastern India. A HEC-HMS model was set up to simulate rainfall–runoff processes for two LULC scenarios three decades apart. Because of sparse data availability at the study site, we used the Natural Resource Conservation Service (NRCS) curve number (CN) approach to account for the effect of LULC and soil on the hydrologic response of the catchment. Although a weak (r=0.53) but statistically significant positive linear correlation was found between sub-catchment wise LULC changes and the magnitude of the flood peak at the catchment outlet, a number of sub-catchments showed marked deviations from this relationship. The varying timing of flow convergence at different stream orders due to localised LULC changes makes it difficult to upscale the conventional land-use and runoff relationship, evident at the plot scale, to a large basin. However, a simple modelling framework is provided based on easily accessible input data and a freely available and widely used hydrological model (HEC-HMS) to check the possible effect of LULC changes at a particular sub-catchment on the hydrograph at the basin outlet. [Copyright &y& Elsevier]

Microplastics are a pollutant of growing concern, capable of harming aquatic organisms and entering the food web. While freshwater microplastic research has expanded in recent years, much remains unknown regarding the sources and delivery pathways of microplastics in these environments. This review aims to address the scientific literature regarding the spatial and temporal factors affecting global freshwater microplastic distributions and abundances. A total of 75 papers, published through June 2021 and containing an earliest publication date of October 2014, was identified by a Web of Science database search. Microplastic spatial distributions are heavily influenced by anthropogenic factors, with higher concentrations reported in regions characterized by urban land cover, high population density, and wastewater treatment plant effluent. Spatial distributions may also be affected by physical watershed characteristics such as slope and elevation (positive and negative correlations with microplastic concentrations, respectively), although few studies address these factors. Temporal variables of influence include precipitation and stormwater runoff (positive correlations) and water flow/discharge (negative correlations). Despite these overarching trends, variations in study results may be due to differing scales or contributing area delineations. Thus, more rigorous and standardized spatial analytical methods are needed. Future research could simultaneously evaluate both spatial and temporal factors and incorporate finer temporal resolutions into sampling campaigns. [Display omitted] • Microplastics are correlated with urban land use, population density, and WWTPs. • Physical watershed and water body characteristics affect microplastic concentrations. • Wet season influences microplastic concentrations via runoff and resuspension. • Different scales of analyses can identify different influences on microplastic pollution. • Spatially explicit analysis is critical to microplastic sources and delivery pathways. [ABSTRACT FROM AUTHOR]

Summary: Impervious surface has been recognized as a key indicator of watershed health and function. The rapid expansion of impervious surface associated with periurban development following the Second World War resulted in concerns that impervious surface would alter flow characteristics, water quality, sediment, and stream morphology. These effects have been documented in studies across many disciplines. Unfortunately, impervious surface is difficult to measure directly, and other forms of land-use data are often substituted as surrogates. This paper highlights the shortcomings in land-use data, particularly parcel-based land-use data, as a surrogate for impervious surface in a periurban environment. Periurban development has changed substantially in the last several decades. This study investigates changes in the form of periurban development in Oakland County, Michigan, from 1945 to 2005, with an emphasis on the accumulation of impervious surface. We first evaluate patterns in the sizes of parcels being developed to residential uses. Using an impervious surface map derived from aerial imagery, we then calculate amount of impervious surface created by different forms of development, both in parcels of similar sizes developed at different times, and across parcel sizes for the period of the study. The results indicate substantial variability in impervious surface within periurban residential development, from 5.4% of parcel area to 25.4% of total parcel area depending on parcel size. Even within relatively specific categories (for example, residential parcels less than 743square metre) impervious surface varied between 18.5% and 34.6% of the parcel area between 1945 and 2000. Since 1980, the trend has been toward larger parcel sizes with lower impervious surface ratios. The overall effect is that land is being developed at a rate substantially greater than the rate impervious surface is being created. The bias created by the trend to larger parcel sizes with smaller impervious surface ratios results in a tendency to overestimate the effects of recent land development. In combination with the change in character of suburban development, this bias has a tendency to overestimate the hydrologic response to new development. This overestimation is easily overlooked because it is consistent with the expected effect of urbanization. However, this effect helps explain observed field results indicating little change in streamflow through time despite significant apparent periurban development. [Copyright &y& Elsevier]

Abstract: This paper aims at developing a methodology for assessing urban dynamics in urban catchments and the related impact on hydrology. Using a multi-temporal remote sensing supported hydrological modelling approach an improved simulation of runoff for urban areas is targeted. A time-series of five medium resolution urban masks and corresponding sub-pixel sealed surface proportions maps was generated from Landsat and SPOT imagery. The consistency of the urban mask and sealed surface proportion time-series was imposed through an urban change trajectory analysis. The physically based rainfall-runoff model WetSpa was successfully adapted for integration of remote sensing derived information of detailed urban land use and sealed surface characteristics. A first scenario compares the original land-use class based approach for hydrological parameterisation with a remote sensing sub-pixel based approach. A second scenario assesses the impact of urban growth on hydrology. Study area is the Tolka River basin in Dublin, Ireland. The grid-based approach of WetSpa enables an optimal use of the spatially distributed properties of remote sensing derived input. Though change trajectory analysis remains little used in urban studies it is shown to be of utmost importance in case of time series analysis. The analysis enabled to assign a rational trajectory to 99% of all pixels. The study showed that consistent remote sensing derived land-use maps are preferred over alternative sources (such as CORINE) to avoid over-estimation errors, interpretation inconsistencies and assure enough spatial detail for urban studies. Scenario 1 reveals that both the class and remote sensing sub-pixel based approaches are able to simulate discharges at the catchment outlet in an equally satisfactory way, but the sub-pixel approach yields considerably higher peak discharges. The result confirms the importance of detailed information on the sealed surface proportion for hydrological simulations in urbanised catchments. In addition a major advantage with respect to hydrological parameterisation using remote sensing is the fact that it is site- and period-specific. Regarding the assessment of the impact of urbanisation (scenario 2) the hydrological simulations revealed that the steady urban growth in the Tolka basin between 1988 and 2006 had a considerable impact on peak discharges. Additionally, the hydrological response is quicker as a result of urbanisation. Spatially distributed surface runoff maps identify the zones with high runoff production. It is evident that this type of information is important for urban water management and decision makers. The results of the remote sensing supported modelling approach do not only indicate increased volumes due to urbanisation, but also identifies the locations where the most relevant impacts took place. [Copyright &y& Elsevier]

Abstract: Wildfires represent an important agent of land degradation in temperate sub-humid ecosystems, including southern European Mediterranean countries. Identification of integrated conservation approaches that can reduce or prevent degradational impacts is the aim of the EU-funded DESIRE research program, part of which is concerned with quantifying the likely benefit of acceptable alternative conservation strategies to wildfire. The overall aim of this paper is to apply a modification of the Pan-European Soil Erosion Risk Assessment (PESERA) model in order to compare predicted soil erosion rates of one possible conservation strategy, the regular application of prescribed fire, with that of wildfire. The model is applied to two fire-prone study areas in central Portugal (Góis and Mação) and predicts runoff and erosion at much larger spatial (regional) and temporal (decadal) scales than is usually possible with field monitoring. Simulation using the model was carried out for 50years based on a historical climate time-series. Even assuming very frequent management burns (every 2years) and infrequent wildfires (100years), the model suggests that this conservation measure can generally reduce soil erosion relative to infrequent wildfires, although the predicted soil losses for both types of fire are large compared even with those obtained from small-scale field monitoring. The benefits, limitations, scope for improvement and application to future climatic scenarios of the model in a fire context are discussed. [Copyright &y& Elsevier]

Abstract: This paper analyzes runoff and soil loss in relation to the rainfall regimes and land use changes in a small mountainous watershed in the Three Gorges Area (TGA) of China. Based on 10years of rainfall measurements and K-means clustering, 152 rainfall events were classified into three rainfall regimes. The mean statistical features of different rainfall regimes display a marked difference. Rainfall Regime I is events of medium amounts (31.8mm) and medium duration (1371min). Rainfall Regime II is events with high amounts (54.0mm), long duration (2548min), and an infrequent occurrence. Rainfall Regime III is events of low amount (22.2mm), short duration (494min) and high frequency. Each rainfall regime results in differing levels of runoff and erosion and Rainfall Regime I causes the greatest proportion of accumulated discharge (368.7mm) and soil loss (4283t). In the different rainfall regimes, the values of the mean runoff coefficient and the mean sediment load were ordered as follows: Rainfall Regime II>Rainfall Regime I>Rainfall Regime III. These results suggest that greater attention should be paid to Rainfall Regimes I and II because they had the most erosive effect. In the Wangjiaqiao watershed, the changes in land use primarily affected the paddy fields, where the cropland decreased significantly and the forest and orchards increased by 9.9% and 7.7%, respectively, during 1995–2004. The ANOVA shows land use changes caused significant decreasing trends in the runoff coefficients (P<0.01) and sediment loads (P<0.01). In order, the most sensitive response of runoff and erosion to land use was Rainfall Regime II>Rainfall Regime>Rainfall Regime III. Rainfall characteristics are decisive for the relative importance of different storm runoff generation mechanisms. The land use changes in the study watershed have considerably decreased runoff and soil loss. [Copyright &y& Elsevier]

Abstract: This paper presents the results of soil hydrological and erosional responses to different land use and cover types in a marginal area of Portugal. The six land uses and vegetation covers studied (cereal crop, fallow land, shrub cover, recovering autochthonous vegetation, land afforested with Pinus pinaster and pastureland) are representative of situations commonly found throughout central and northern Portugal and also in other Mediterranean systems. The specific goals were to evaluate and compare the hydrological and erosional response of soils representing different land uses and vegetation types, to establish the influence of climatic variability and soil surface characteristics, and to assess the efficiency of alternative land uses proposed by the Common Agrarian Policy in terms of hydrogeomorphic behaviour. The results show significant hydrogeomorphic responses among land uses/covers, indicating arable land and coniferous afforestation as the most serious in terms of runoff and soil erosion. With these types of land use, the soil transported by runoff peaks during autumn/winter coincided with the highest and most erosive rainfall in the experiment area. Conversely, shrub cover and recovering oak, resulting from land abandonment and plant succession, and pastureland, as consequence of conversion to arable land, showed the greatest rainfall infiltration capacity and the lowest rate of soil erosion. According to the results, vegetation dynamics emerges as a key factor in quantifying and interpreting the hydrological and erosional response of the land use/covers monitored. Soil erosion can subsequently be controlled by changing land use and increasing the ground cover, which was revealed as one of the basic approaches to controlling soil erosion in all types of land use. [Copyright &y& Elsevier]

Abstract: An increasing number of studies have indicated that soil erosion, sediment redistribution and water discharge during the Holocene have varied greatly under influence of environmental changes. In this paper we have used a modeling approach to study the driving forces for soil erosion and sediment redistribution on the one hand, and water discharge on the other hand, during the Holocene for the Belgian Dijle catchment. Soil erosion and sediment redistribution was modeled using the spatially distributed Watem/Sedem model. Several scenarios of past land use and climate were used to model soil erosion, colluvial sedimentation and sediment export to the fluvial system, and those scenarios were combined with a sensitivity analysis. Modeling results are validated based on an available time differentiated field-based sediment budget. Water discharge was modeled using the spatially distributed STREAM model with a daily time step. The model was calibrated based on contemporary discharge data. The results indicate that soil erosion has increased between the early Holocene and the current situation by ca. 9% due to climatic variations, and by ca. 6000% due to changes in land use. The average discharge has increased by ca. 7%, mainly due to land use changes, and the discharge also shows more peaks. The decrease in cropland area and increase in built up area since 1775 CE has resulted in a decrease in soil erosion and in a further increase in discharge, showing the difference in sensitivity of both processes to land use changes. [ABSTRACT FROM AUTHOR]

Abstract: Erosive runoff is a recurring problem and is a source of sometimes deadly muddy floods in the Pays de Caux (France). The risk results from a conjunction of natural factors and human activity. Efficient actions against runoff in agricultural watersheds are well known. However they are still difficult to implement as they require co-operation between stakeholders. Local actors thus need tools to help them understand the collective consequences of their individual decisions and help to initiate a process of negotiation between them. We decided to use a participatory approach called companion modelling (ComMod), and, in close collaboration with one of the first group of local stakeholders, to create a role-playing game (RPG) to facilitate negotiations on the future management of erosive runoff. This paper describes and discusses the development of the RPG and its use with other groups of local stakeholders within the framework of two game sessions organized by two different watershed management committees. During the joint construction step, stakeholders shared their viewpoints about the environment, agents, rules, and how to model runoff in preparation for the creation of the RPG. During the RPG sessions, two groups of eight players, including farmers, mayors and watershed advisors, were confronted with disastrous runoff in a fictive agricultural watershed. Results showed that they managed to reduce runoff by 20–50% by engaging a dialogue about grass strips, storage ponds and management of the intercrop period. However, further progress is still needed to better control runoff through the implementation of better agricultural practices because, during the RPG sessions, the watershed advisors did not encourage farmers to do so. Because of the complexity of management problems, results of jointly constructing the game and the RPG sessions showed that modelling and simulation can be a very useful way of accompanying the collective learning process. This new way of working was welcomed by the participants who expressed their interest in organizing further RPG sessions. [Copyright &y& Elsevier]

Abstract: Urban sprawl is considered by most environmental scientists and urban planners to be a serious environmental problem. However, public perception about parking availability often forces planning offices to recommend parking lot sizes that exceed daily demands. The recent trend of increasing the size of stores, churches and even schools comes with increasing the size of parking lots that service these buildings. The objective of this paper is to analyze space allocation of parking lots in a typical midwestern county and to estimate the supply of parking spaces to potential demand. We also estimate the loss of ecosystem services represented by the area of parking lots in this county. We found that parking lots cover 5.65km2 (1 397acres) of Tippecanoe County, Indiana which implies that 0.44% of the county area is devoted to parking lots. Our results show that there are approximately 2.2 parking spaces per registered vehicle, that parking lots make up more than 6.57% of the total urban footprint in this county, that the area of parking lots exceeded the area of parks in the city limits by a factor of three and that parking lot runoff and pollutants are significant compared to runoff and pollutants from these areas prior to their conversion to parking lots. As other authors have done before us we lament the poor use of land in urban regions of the United States, and encourage planners to think creatively about the use of land for parking. [Copyright &y& Elsevier]

Summary: Nutrient transport in surface runoff associated with sediment constitutes an important nutrient loss in Tigray, Northern Ethiopia, but little information is available on this aspect. This paper analyses runoff coefficient, runoff volume, sediment yield and sediment-associated nutrient losses under different land uses (cultivated, grazing, eucalyptus plantation, and exclosure lands) in the Tigray highlands. Two years data on rainfall, runoff volume, sediment yield and sediment-associated nutrient losses were collected from 31 runoff plots of 20m2. Results show that runoff coefficient, runoff volume and sediment yield are significantly higher in cultivated land than in the other land uses. On average, runoff volume from cultivated land is two times higher than in open grazing land at Gum Selassa, but at Maileba it is 5, 6, 16 times higher than in plantation, open grazing, and exclosures, respectively when extreme rainfall events were excluded. The respective values for sediment yield from cultivated land at Maileba are 4, 5 and 27 times higher. Variation in total rainfall amount that produced runoff explained 69% of the annual runoff volume variability, and this in turn explained 76% of the annual sediment yield variability. Among the plot variables, vegetation ground cover was significantly and negatively correlated with runoff coefficient; and runoff generation tends to be negligible when the ground cover exceeds 72%. Concentration of sediment-associated nutrient losses decreased with increasing sediment yield, supposedly related to the important nutrient dissolution effect of high runoff volumes. Rainfalls with low amount and intensity are important for selective removal of nutrient-rich sediments. Annually, on average, nutrient and OC losses varied between 14.4 and 263.4kgha−1 y−1 for OC, 2.1–32.8kgha−1 y−1 for N, 0.02–0.2kgha−1 y−1 for available P and 0.35–5.25kgha−1 y−1 for available K, with the lowest values in all cases on exclosures and highest on cultivated land. The present study demonstrates the effectiveness of exclosures and plantation in controlling runoff, sediment and sediment-associated nutrient losses on steep degrading lands of the region. [Copyright &y& Elsevier]

This paper introduces a simple two-layer soil water balance model developed to Bridge Event And Continuous Hydrological (BEACH) modelling. BEACH is a spatially distributed daily basis hydrological model formulated to predict the initial condition of soil moisture for event-based soil erosion and rainfall–runoff models. The latter models usually require the spatially distributed values of antecedent soil moisture content and other input parameters at the onset of an event. BEACH uses daily meteorological records, soil physical properties, basic crop characteristics and topographical data. The basic processes incorporated in the model are precipitation, infiltration, transpiration, evaporation, lateral flow, vertical flow and plant growth. The principal advantage of this model lies in its ability to provide timely information on the spatially distributed soil moisture content over a given area without the need for repeated field visits. The application of this model to the CATSOP experimental catchment showed that it has the capability to estimate soil moisture content with acceptable accuracy. The root mean squared error of the predicted soil moisture content for 6 monitored locations within the catchment ranged from 0.011 to 0.065cm3 cm−3. The predicted daily discharge at the outlet of the study area agreed well with the observed data. The coefficient of determination and Nash–Sutcliffe efficiency of the predicted discharge were 0.824 and 0.786, respectively. BEACH has been developed within freely available GIS and programming language, PCRaster. It is a useful teaching tool for learning about distributed water balance modelling and land use scenario analysis. [Copyright &y& Elsevier]

Abstract: Tropical mountain regions are affected by rapid land use/-cover change, which may threaten their (eco-)hydrological functions. Although there is a growing interest in evaluating the effect of land use/-cover change on mountain hydrology, quantitative assessments of the impact of land use/-cover on hydrological processes are hampered by the lack of field measurements characterizing runoff generation processes. In this paper, we present results from field experiments of rainfall runoff mechanisms in the southern Ecuadorian Andes. A rainfall simulator was used to quantify the hydrological response of distinct land use/-cover types to intense rainfall (about 40 mm/h). The rainfall runoff experiments indicate that degraded and abandoned land generate surface runoff within a few minutes after the start of the rainfall event. These lands have a very rapid and sharp hillslope hydrological response, as Hortonian overland flow is the dominant runoff generation mechanism. In contrast, surface runoff on arable and rangelands is rare, as their soils are characterized by a high infiltration capacity (i.e. >29 mm/h). Our experiments provide evidence that runoff generation in degraded Andean ecosystems is mainly controlled by the surface vegetation cover and land management. When reducing the surface vegetation cover, the soil is increasingly affected by rapid hillslope runoff as the presence of large amounts of smectites in the outcropping soft rocks makes the material very prone to sealing and crusting, thereby enhancing runoff generation. [Copyright &y& Elsevier]

Abstract: Over the last 30 years, European agricultural policy has influenced agricultural practices. These have led to an increase in numerous environmental issues such as the erosion and runoff risk, which have reached an alarming level in loamy soils of Upper Normandy. To control runoff and erosion at catchment scale, public authorities need tools in order to obtain a better knowledge of present or future pressure on the environment. With such information, it will be easier to act locally on a problem by avoiding negative impacts elsewhere in the area. Numerous models have been developed to assess the impacts of land-use modifications. This paper presents a brief description of the remote sensing version of STREAM, called STREAM-TED, which then is used to estimate and map runoff according to various scenarios of rain event and land-use distribution in a cultivated catchment. Three kinds of scenarios of land-use modifications have been considered: partial or complete reduction of grassland in favour of cash crops, modifications of agricultural practices on arable lands, and insertion of water management on the catchment. Results of 11 management scenarios tested showed the negative effect of a partial or complete ploughing of permanent grassland. Changes on arable land scenarios showed that these modifications reduced runoff in various ways according to rainfall events. The scenario with the most significant impact consists of simulating the introduction of 100% more environmentally friendly production methods on arable lands. With this scenario, runoff is practically eliminated for winter rainfall events and is decreased twofold for summer rainfall events. In addition, it is the only scenario which leads to a significant runoff volume reduction even with a “catastrophic” rainfall event. [Copyright &y& Elsevier]

Overland flow and soil erosion models working with coarse to medium resolution input data for prediction on large areas often rely on high resolution calibration and evaluation datasets collected for smaller areas. Therefore, one important issue is to assess to what extent process identification and parameterisation carried at one scale can be extrapolated to a different scale. The objective of this paper is to identify the nature and the cause of variation in the runoff response for areas ranging from plots to 10 km2 catchments on the basis of extensive multi-scale field information gathered on arable lands of the loam belt in Northern France. Three datasets are studied: data from plots of ca. 500 m2 consisting of either 100 or 90% arable land; data from a catchment of ca. 90 ha with either 96 or 94% arable land; and data from a catchment of ca. 1100 ha with ca. 80% arable land. For the three datasets mean slope gradient and soil types are similar. Between the three datasets, a significant decrease in the runoff coefficient is observed as the area increases. This trend, which has already been observed by many researchers, confirms that a catchment cannot be considered as the sum of individual fields. A simple distributed approach, based on the dominant processes, that defines the infiltration parameters at the field scale (allowing reinfiltration) and accounts for natural or human induced preferential pathways within the catchments could reproduce the observed runoff coefficients. In this context, the scaling transition between the plots and the 10 km2 catchment can thus be considered in terms of connectivity between the ‘infiltrating’ and ‘runoff producing’ areas. However, if we select data with contrasting land use for the three datasets, it shows that the variations between the different runoff coefficients can be smoothed out or accentuated. Furthermore it demonstrates the importance of possessing a database that covers a large range of situations when studying spatial scaling linkages in order to be able to distinguish between the different factors. Finally these results are compared with results from a study where rainfall–runoff events were simulated on 40 selected catchments of ca. 10 km2 in Hte-Normandie (France). For catchments of this scale, it appears that the percentage of arable land is a driving factor in the runoff response whatever its location within the catchment. One explanation being that connectivity variability can be significant between the plot scale and the catchment scale but is relatively less important between different 10 km2 cultivated catchments. [Copyright &y& Elsevier]

Systems including a long fallow period have proven to be sustainable in the tropics for they enable the transfer of the rich store of nutrients from the vegetation to the ensuing crops. These systems have been mainly studied in the forest zone with a peculiar focus on the maintenance of organic and chemical fertility. By contrast, the effects of the fallow on soil physical properties have not been widely documented especially in the drier areas. The objectives of this paper are: (i) to summarise the fragmented and not readily accessible information on the responses of soil crusting, runoff, water and wind erosion to fallowing in the sub-humid and semi-arid regions of West Africa; (ii) to infer possible scenarios of land use change from the recent past. Two main examples have been taken in northern Ivory Coast and southern Niger. In the Ivorian example, physical properties are restored after a fallow duration of 10 years on sandy clay loam whilst crusts persist over a longer period on sandy soils, partly due to the foraging activities of termites. In the sandy Sahelian soils, cultivation destroys the erosion crusts that develop as the fallow proceeds as a result of dust deposition and colonisation by blue green algae. This crust development is inherent to the Sahelian ecosystem and favours the natural concentration of water resources. The net balance of dust is negative in millet fields (-0.25 t ha-1 per year) and positive in young fallows (+0.68 t ha-1 per year) so that a slight increase in the field/fallow ratio can transform the region from an accumulation zone to a source zone with consequences on regional fertility transfer. Finally, in both regions the sandy soils have specific dynamics that should be accounted in land management planning. Despite a higher water erosion risk, the sub-humid zone offers a better potential for intensification than the semi-arid zone. [Copyright &y& Elsevier]

The paper illustrates impact studies of land use changes on the water balance in meso and macroscale river basins. Problems of impact studies in large river basins result mainly from a huge heterogeneity inside and the relative rough input database. Simple approaches are needed to setup possible land use changes on the basis of easily available spatial data. The investigations are carried out for the river basins of the Saale (24 000 km2) and the Havel (19 000 km2), two main tributaries of the Elbe River. The hydrological simulations were done with the modelling system ArcEGMO (Becker et al., in: Mathematical Models of Watershed Hydrology, Water Resources Publications, Littleton, CO, 2002). [Copyright &y& Elsevier]

• Derivation of analytical flood frequency distributions. • Derived equations improve the capabilities of the analytical probabilistic models. • Analytical probabilistic models are suitable for urban stormwater management. • The analytical models can reflect rainfall conditions at different locations. Derived flood frequency models developed specifically for urban stormwater management purposes are referred to as analytical probabilistic stormwater models. These models use closed-form analytical equations to estimate flood frequencies under various land use conditions which facilitate quick analysis of different design alternatives. In this paper, in order to further improve the capability of the analytical probabilistic models, additional analytical expressions relating a catchment's peak discharge rate to its physical characteristics and the local rainfall statistics are derived considering saturation-excess in addition to infiltration-excess runoff generation and various possible hydrograph shapes. These analytical expressions along with the frequency distributions of the input rainfall event volume and duration are used to develop a new derived flood frequency model suitable for catchments where saturation-excess runoff generation is possible. An example application of the new model to a test catchment in Hamilton, Ontario, Canada is illustrated to verify the accuracy of the new model. Assuming hypothetically that the same catchment is instead located at several other places in the United States, the reliability of the analytical probabilistic models under different climatic conditions is verified as well. [ABSTRACT FROM AUTHOR]