Land use, water management and future flood risk.

The first flush load of urban surface runoff

Recent developments in flood modeling have led to the concept of coupled (sewer/surface) hydraulic models. In this paper two coupled models are examined; a one-dimensional (1D) sewer model coupled with a 1D surface network model (1D/1D) and a 1D sewer model coupled with a two-dimensional (2D) surface flow model (1D/2D). Flow over the terrain is better modeled by 2D models, whereas in confined channels 1D models provide a good approximation with less computational effort. This paper presents a comparison of the simulation results of 1D/1D model and a 1D/2D model. The methodology adopted for setting up the models is outlined and explained in detail as well as the 1D/1D modeling techniques used for reproducing the 1D/2D model results. The surface flow comparison clarifies the limitations of the 1D/1D model and indicates that the definition of the surface pathways, the linking elements sewer/surface, and inclusion of virtual manholes are key factors for setting up a more accurate 1D/1D model.

Comparison of 1D/1D and 1D/2D Coupled (Sewer/Surface) Hydraulic Models for Urban Flood Simulation

http://eprints.qut.edu.au/4696/1/4696.pdf

Analysis of heavy metals in road-deposited sediments.

Continuous water quality measurements of storm runoff into a single road inlet have been carried out at two experimental catchments in Belgrade, Yugoslavia, and Lund, Sweden. Both sites were equipped with similar instrumentation for measurements of overland flow, turbidity, pH, conductivity, and temperature. The data were recorded at 10-s time intervals during rainfall events. To measure suspended solids concentration, turbidity meters were calibrated in conditions very similar to the real world. A detailed description of the field-measuring facilities used in the Belgrade catchment and the results of the measurements from both sites are presented. After detailed examination of possible errors in measurement, only the reliable data were used for statistical analysis. Event mean, extreme, and aggregated values were analyzed. The results indicate that the antecedent dry weather period length has only a minor effect upon road sediments wash-off, but it has an influence upon conductivity. The "first-flush effect" of suspended solids appears only in a limited number of events. Cross-correlation coefficients of rainfall, overland flow, and water quality were calculated for each event, taking into account the time lag between observed characteristics. These coefficients showed that suspended solids loading rate is influenced by rainfall intensity and overland flow rate. The results presented in this paper have been used in development of the physically based wash-off model published by Deletic and colleagues.

Evaluation of Water Quality Factors in Storm Runoff from Paved Areas

SIPSON--simulation of interaction between pipe flow and surface overland flow in networks.

A mathematical model of suspended solids discharge from impervious surfaces during storm events has been developed. The model continuously simulates two major processes of different time scales; solids build-up at impervious surfaces between two storm events, and solids wash-off from the surfaces during storm events. Buildup is modelled using the Sartor and Boyd equation (21) in which the amount of' solids available on the surface is an exponential function of antecedent dry weather period duration. The spatial distribution of solid particles over the street surface is also modelled, which is an innovation. The wash-off process is divided into three subprocesses that are modelled consecutively. A kinematic wave model is used for overland flow modelling. The particle entrainment into suspension is estimated by two methods. In one, the rainfall and overland flow effects are not separated and the total shear stress is used to predict entrainment. In the other, the rainfall and overland flow effects are treat...

Modelling of storm wash-off of suspended solids from impervious surfaces

One of the most important steps in the development of water distribution system simulation models is providing the dependence of results of simulation on the uncertainty of input values. Information about propagation of uncertainty through the simulation model provides a basis for general model improvement in an efficient and economic (low cost) way. Besides statistically based uncertainty and sensitivity analyses, the fuzzy set theory provides an alternative that does not require crisp statistical measures of input parameter distributions. Uncertainty is represented by fuzzy set parameters, which do not have direct correspondence with statistical background, although indications of uncertainty can be easily recognized. In the analysis presented in this article, applied to the model water distribution system of the Becej community, roughness of old pipes has been selected as the uncertain parameter, as the correct values and their statistical distribution are unknown. As fuzzy uncertainty analyses for non...

Fuzzy approach in the uncertainty analysis of the water distribution network of Becej

In water distribution network (WDN) modelling, nodal demand is the sum of flows taken by users associated with a computational node. User demands are not fixed in time; rather they are stochastic. Hence, nodal demand is a model parameter with high uncertainty, which is propagated throughout the WDN model, thus also rendering the output values (node pressures and pipe discharges) uncertain. Total water inflow into the network can be accurately measured using flow meters. This paper investigates how knowledge of system inflow can be used as a constraint in WDN modelling, taking into consideration the uncertain nodal demands, and consequently reducing the uncertainty of the model output. Fuzzy sets were used to represent the uncertain demands and modified genetic algorithms were used to find the optimal solutions. As a test case, a set of data from a real WDN was used. The uncertainty of the WDN model output was computed for two cases: first, with the total network inflow taken into consideration; and second...

Uncertainty reduction in water distribution network modelling using system inflow data

The determination of the capacity, location and configuration of a pumping station has to be based on a detailed analysis of the proposed system. Factors like forecasted demand, available supply, function of the pumping station in the water supply system etc., have to be thoroughly considered. Due to these requirements pumping stations in water supply systems (WSS) almost exclusively have more than one pump, and lots of other devices and equipment required for correct operation. In this analysis, however, only the schematic representation of pumping stations will be used (for example, Figure 1.) and equipment relevant for mathematical modelling of transient flow will be indicated.

Marko Ivetić

Papers

SIPSON--simulation of interaction between pipe flow and surface overland flow in networks.

Modelling of storm wash-off of suspended solids from impervious surfaces

Fuzzy approach in the uncertainty analysis of the water distribution network of Becej

Uncertainty reduction in water distribution network modelling using system inflow data

Pumping Stations and Transient Flow Analysis