Abstract:Numerical tests indicate that Hortonian runoff mechanisms benefit from scaling effects that non-Hortonian runoff mechanisms do not share. This potentially makes Hortonian watersheds more amenable to physically based modelling provided that the physically based model employed properly accounts for rainfall distribution and initial soil moisture conditions, to which these types of model are highly sensitive. The distributed Hortonian runoff model CASC2D has been developed and tested for the US Army over the past decade. The purpose of the model is to provide the Army with superior predictions of runoff and stream-flow compared with the standard lumped parameter model HEC-1. The model is also to be used to help minimize negative effects on the landscape caused by US armed forces training activities. Development of the CASC2D model is complete and the model has been tested and applied at several locations. These applications indicate that the model can realistically reproduce hydrographs when properly applied. These applications also indicate that there may be many situations where the model is inadequate. Because of this, the Army is pursuing development of a new model, GSSHA, that will provide improved numerical stability and incorporate additional stream-flow-producing mechanisms and improved hydraulics.

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The ability of green roof systems to impact stormwater runoff from buildings has been covered in many research studies. However, a lot of these studies looked at long-term retention, with much less work focused on how to model a green roof's response to larger design storms. Work that has examined flow routing for individual rainfall events has focused on empirical routing models that are tuned to the specific roof being modelled. This paper presents a new physics-based model for flow routing based on the green roof module geometry and soil properties, which requires only a single discharge coefficient to be measured. The results of this model were compared with the results of a series of experiments to quantify a modular green roof system's hydraulic response to drawdown and steady rainfall.

We describe effects of a range of fallow and crop management practices on soil properties and crop growth in wheat and grain sorghum on a red-brown earth in south-west Queensland. Results from the first 4 years of the experiment, which commenced in 1983, have been published. This paper reports results from the next 6 years. No tillage (NT) and reduced tillage (RT), combined with stubble retention, resulted in better soil-water storage during fallow but less soil nitrate-nitrogen (N) at sowing than observed with more frequent and aggressive mechanical tillage treatments such as discing, and stubble removal. In drier growing seasons, when N application often resulted in yield reductions in wheat, NT and RT with stubble retention resulted in higher grain yields than other treatments in both crops. In a wetter growing season, when N application resulted in yield increases, wheat yields under NT and RT with stubble retention were lower than those of other treatments, even at the highest rate of N application, indicating that factors such as plant disease were also affecting yields. With stubble retention, average yields of 6 wheat crops were 12% higher under NT and reduced blade tillage, and average yields of 4 sorghum crops were 20-30% higher under NT, than other tillage treatments. Gypsum application resulted in an average yield increase of 15% in both crops under conventional disc tillage with stubble retention. In wheat, NT and RT with stubble retention were generally associated with lower grain protein concentration, and N application was necessary to maximise profitability of these practices.