Caterina Valeo

Relationship between wadi drainage characteristics and peak-flood flows in arid northern Oman

Abstract Relationships between watershed characteristics and mean wadi flood peaks in arid regions are investigated. Mean flood peak discharge was derived for 12 watersheds ranging from 64 to 1730 km2 in Oman using 270 flood events from 10 years of record. Fourteen watershed characteristics were automatically extracted from a digital elevation model, and multiple regression was used to investigate the effect of these characteristics on wadi mean peak flow (Q MPF) and 5-, 10-, 20-, 50- and 100-year return period flood peaks. Drainage area (DA), wadi slope (WS), watershed mean elevation (BE) and agricultural/farm area (FR) were found to be the key variables affecting flood flows. As return period increased, the influence of BE on flood-peak estimation decreased. In addition, urbanization is increasing alongside increasing agricultural areas, and the inclusion of FR in the relationship improved the variance explanation by 11% over models using only traditional variables such as DA and BE. Citation Al-Rawas, G. A. & Valeo, C. (2010) Relationship between wadi drainage characteristics and peak flood flows in arid northern Oman. Hydrol. Sci. J. 55(3), 377–393.

Climate Change Impacts in the Elbow River Watershed

The Elbow River Watershed originates in the foothills of the Rocky Mountains and is a primary source of water for the City of Calgary. Consequently, the long-term protection and investment of this resource is a primary interest to the City of Calgary. While droughts and water shortages are a serious concern to Albertans, spring freshet flooding may lead to enormous costs virtually overnight. The impacts of climate change on spring flooding in the Elbow River Watershed were determined using both a statistical analysis of historical hydro-climatological data and a modelling analysis using the Canadian Regional Climate Model (CRCM) forcing to the SSARR Watershed model, which is used by Alberta Environment for flood forecasting. Statistical analyses revealed that there were significantly increasing trends in annual mean temperature in the eastern most part of the watershed (+0.007°C/yr) caused by significant trends during February and March only. Significantly increasing trends in annual mean temperature in the western portion of the watershed were also observed (+0.056°C/yr) and were primarily due to increases in January, March, April, July and August. There were no demonstrated trends in total annual precipitation but significant decreases in snowfall were observed in the eastern portion of the watershed. Conversely, increases in snowfall were observed in the western portion near the foothills. No significant trends were observed in discharges within this watershed. Modelling spring freshet flooding using the SSARR and CRCM models showed that spring time flooding due to expected increases in precipitation during the month of May can nearly double flood peaks.

Characterizing Physicochemical Quality of Storm-Water Runoff from an Urban Area in Calgary, Alberta

Understanding storm-water runoff quality is required to develop effective urban storm-water runoff management for regions of semiarid climate. In this study, the quality of storm-water runoff from a semiarid, urban residential catchment, draining through separated storm-water sewers was investigated in 2006 and 2007. Water temperature, conductivity, pH, dissolved oxygen, and turbidity were continuously measured during 16 storm events. Storm-water runoff quality was characterized in terms of event mean values (EMVs), loads, and first flush (FF) loads and their relationships with rainfall characteristics. Discharge of total suspended solids (TSSs) is in general governed by the flow magnitude in storms and no significant relationships exist between the FF loads of TSS and rainfall intensity. The discharge of dissolved solids is independent of the flow magnitude. Strong FF effect for dissolved solids and weak FF effect for TSS were observed. This semiarid region provided no relationship between the EMVs of both TSS and conductivity and the antecedent dry period. This raises doubts on storm-water runoff being more heavily loaded with pollutants after a longer dry period in semiarid regions.

Influence of forest fires on climate change studies in the central boreal forest of Canada

This brief paper indicates that forest fires may have short and longer term effects on runoff and thus, can influence trend studies on the response of watersheds to climate change. Twenty-two watersheds at the Experimental Lakes Area in northwestern Ontario were studied to view the impacts of climatic variability and forest fires on runoff. A roughly 30 year database demonstrated few trends in climatological variables and even fewer trends in runoff data at the 5% significance level. Daily maximum temperature increased by 0.053 °C per year, while precipitation in the months of February and March showed significant decreases. Total snow showed a significant decrease over a 30 year period at the 8% significance level. The Mann Kendall test for trend was applied to the runoff indices of 19 watersheds and it was revealed that only six exhibited trends. Of these, five had been burned during the test period. Virtually all burned watersheds showed initial increases in runoff, however, long term runoff trended lower in the burned watersheds, while the one watershed that was not burned showed an increasing trend. Forest fires alter the age distribution of trees with subsequent impacts on water yields in the short and longer term.

Characteristics of suspended solids, microorganisms, and chemical water quality in event-based stormwater runoff from an urban residential area.

Temporal evolution of microbiological, physical, and chemical quality of stormwater runoff from a stormwater drain in an urban residential area in Calgary, Canada, was investigated from May to September, 2006 and 2007. Investigating event mean concentrations and their correlations with rainfall characteristics revealed that intensive rainfall events produced highly polluted stormwater runoff when pollutant source limitation did not occur. Inconsistent event-based correlations between total suspended solids (TSS) concentrations and water quality parameters were observed. During storms, the loading of TSS exhibited a flow-dependent nature, whereas microorganism discharge appeared to be governed by a flow-independent mechanism. No strong first-flush effect was observed in either TSS or microorganisms, on average. No correlations of first-flush loads of TSS with rainfall characteristics were identified. Moderate negative correlations between first-flush loads of microorganisms and rainfall depth and intensity indicated that first flush of microorganisms tended to occur in small storms.

A new fuzzy linear regression approach for dissolved oxygen prediction

Abstract A new method for fuzzy linear regression is proposed to predict dissolved oxygen using abiotic factors in a riverine environment, in Calgary, Canada. The proposed method is designed to accommodate fuzzy regressors, regressand and coefficients, i.e. representing full system uncertainty. The regression equation is built to minimize the distance between fuzzy numbers, and generalizes to crisp regression when crisp parameters are used. The method is compared to two existing fuzzy linear regression techniques: the Tanaka method and the Diamond method. The proposed new method outperforms the existing methods with higher Nash-Sutcliffe efficiency, and lower RMSE, AIC and total fuzzy distance. The new method demonstrates that nonlinear membership functions are more suitable for representing uncertain environmental data than the typical triangular representations. A result of this research is that low DO prediction is improved and consequently the approach can be used for risk analysis by water resource managers. Editor D. Koutsoyiannis; Associate editor T. Okruszko

Investigation of the MODIS snow mapping algorithm during snowmelt in the northern boreal forest of Canada

A major limitation in mapping snow-covered area (SCA) when using optical satellite sensors is encountered in forested areas, particularly during snowmelt. Consequently, using land cover information to map snow in heterogeneous environments that include dense forest might provide a solution. This study investigated the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center version 4 snow mapping algorithm developed for the moderate resolution imaging spectroradiometer (MODIS) Terra sensor. The functionality of this algorithm for mapping snow during the snowmelt period in the northern boreal forest of Manitoba was tested by comparing the results of this algorithm with those produced by two other algorithms that rely on land cover data instead of the normalized difference vegetation index (NDVI). Comparisons are also made between these three algorithms and the SCA provided by the MOD10A1 MODIS Terra product. For the 2001 snowmelt period, the results from the algorithms and the Terra product showed no noticeable difference in the amount of SCA predicted, but a difference of as much as 20% existed over the 2002 melt period, with the MODIS product predicting more snow than the algorithms. Atmospheric corrections and thresholds used to detect dark targets also had noticeable influences on the amount of SCA predicted by the algorithms. The location of areas mapped with snow also differed between the algorithms and the MOD10A1 product. The agreement in the location of SCA between that predicted by the algorithms and that provided by MOD10A1 differed by as much as 75% towards the end of the 2001 melt period, and even larger discrepancies were observed in 2002. Analysis indicated that the greatest differences occurred in marsh and coniferous areas, and this was consistent throughout the melt period. In addition, higher elevations caused the greatest differences in early stages of the melt period, but lower elevations contributed to the differences in later stages of melt. SCA data for both years showed an exponential correlation with accumulated degree-days for 2001, 2002, and 2003, but the relationship varied depending on the length of the melt period. Snow depletion behavior at different elevation ranges in the study area indicated that snow located at higher elevation ranges melted faster than snow located at lower elevation ranges for 2001, 2002, and 2003. This analysis is based on the MODIS Terra version 4 snow mapping algorithm (as opposed to the algorithm used for the MODIS Aqua sensor), and it is still the most up-to-date version as of early 2006.

Environmental Hydraulics: Hydrodynamic and Pollutant Transport Modelling of Lakes and Coastal Waters

Preface 1. Introduction 2. The Mathematical Theory of Circulation Models 3. The Vertically-Integrated Two Dimensional Models 4. Three-Dimensional Circulation Models 5. Quasi Three Dimensional Circulation Models 6. Particle Trajectory and Pollutant Transport Models 7. Numerical Analysis of Coarse Fine Grid Models 8. Model Verifications with Analytical Solutions and Laboratory Data 9. Model Applications to the Great Lakes 10. Model Applications to Other Lakes and Coastal Waters 11. The Future in Hydrodynamic Modelling References Appendix Subject Index

Three Types of Permeable Pavements in Cold Climates: Hydraulic and Environmental Performance

AbstractThis paper examined and compared the hydraulic and environmental performance of permeable interlocking pavers (PICPs), porous asphalt (PA), and porous concrete (PC) under cold climate conditions in Calgary, Alberta, Canada. Assessments were made of their hydraulic performance in terms of storm runoff reduction and surface infiltration capacity, and environmental performance in terms of the removal of several pollutants including total suspended solids (TSS), total nitrogen (TN), total phosphorous (TP) and, heavy metals: copper (Cu), lead (Pb), and zinc (Zn). Results from this paper demonstrated that PA, PC, and PICPs are all effective in mitigating storm runoff under cold climate conditions. Surface infiltration rate was substantially affected by winter sanding materials for PA, PC, and PICPs. Pressure washing was demonstrated to be able to partially restore surface infiltration rates for all three types of pavements. All pavement types in general have the same level of performance in removing TSS...

Effects of urban form on wadi flow frequency analysis in the Wadi Aday watershed in Muscat, Oman

The effect of urban form on Curve Number (CN) use in rainfall-runoff modelling is explored in an arid wadi watershed in Oman. The standard hydrologic CN used in the Soil Conservation Service method may not be appropriate to use in urbanized arid wadi regions since the land-use characteristics are different than those for which the CN method was developed for. In this paper a new method is described to develop regional CN for arid wadi regions. The modified CN are then used to predict peak-flow and time-to-peak in a wadi watershed and are compared to results from the standard CN method. The regional values produce higher peak-flow (an increase of 19% or 7.4 m3/s, on average) with shorter time-to-peak (a decrease of 16% or 86 minutes, on average), mimicking the flash-floods seen in the region. In addition, the regional CN were used to model the change in hydrology caused by urbanization.