Basin lag time is an important variable in the calculation of peak discharge resulting from a specified precipitation input. For the case of ungauged basins, the lag time must be estimated, normally from one or more expressions relating lag time to basin physical characteristics. A number of such expressions exist but each was developed for a particular range of basin size and geographic region. To overcome the problem of using an expression that may not be appropriate, a tentative general expression for basin lag time has been developed using data from basins representative of many regions in North America and ranging in area from 0.5 ha to 5840 km2. The tentative expression has only one basin characteristic, basin length divided by the square root of basin slope, [Formula: see text], and applies to natural basins with minimal effective lake and swamp storage. When more data become available, the expression will be modified to include the effects of urban development and significant storage. Key words: lag time, peak discharge, prediction equation, ungauged basins.
Extreme rainfalls in southern Ontario may increase significantly as a result of climate change. This study was designed to determine the impact of a 15% increase in design rainfall intensities on drainage of a typical urban catchment and to investigate adaptive measures. A calibrated model (PCSWMM 2000) was used to: (1) determine the system performance under current and climate-changed design rainfalls; and (2) calculate the magnitudes of various adaptive measures required to reduce the peak discharge to current levels. For this type of catchment, effective retrofit options that provide the required peak discharge reductions included downspout disconnection (50% of connected roofs), increased depression storage (by 45 m3/impervious hectare), and increased street detention storage (by 40m3/impervious hectare).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.