Usman T. Khan

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

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.

Response of green roof performance to multiple hydrologic and design variables: a laboratory investigation

Multiple factors affect green roof performance and their effects might vary at different stages of operation. This paper aimed to link green roof performance to hydrologic variables (antecedent moisture condition (AMC) and rainfall intensity) and design variables (growing medium (GM) type and depth) under multiple dimensions at the early stage of operation using laboratory experiment data. The results showed that the AMC is the most influential factor of hydrologic performance, whereas the GM type appeared to primarily affect the nutrient levels of the outflow. The significant main effects of other variables and interaction effects between two variables point to challenges in green roof design.