Bruce M. McEnroe

Calibration of Storm Drainage Design Inputs for a Small Urban Watershed

Storm-drainage design inputs such as lag times, times of concentration and rational runoff coefficients should be calibrated with local gaging data wherever possible. This paper documents the calibration of these inputs for the 170-acre Wilshire Woods watershed in the Kansas City metro area. The watershed is 33% impervious with curb-and-gutter streets, storm sewers, and a short segment of open channel. We determined the basin lag time by calibrating a simple watershed model with detailed rainfall and water-level data for 28 significant runoff events from the 13-year record. These calibrations yielded a lag time of 6 minutes and a corresponding time of concentration of 10 minutes. We performed a discharge-frequency analysis on the series of annual peak flows, and computed rational C values from the discharges and 10-minute rainfall intensities. We obtained rational C values of 0.42, 0.50, 0.52 and 0.54 for return periods of 2, 5, 10 and 25 years.

The Rosgen rosetta stone: translating rosgen terminology.

David Rosgens methods for river classification, analysis, and restoration design have been utilized to varying extents all over the United States. A growing body of geomorphic data is being collected by individuals trained in Rosgen methodologies. While this information can be extremely valuable for geomorphic analysis, it can be easily misapplied. Rosgen assigns unique definitions to common terms and uses special methods that differ from the definitions and methods used in traditional geomorphology, hydrology and hydraulics. Researchers and agencies using geomorphic data collected by Rosgen-trained surveyors need to understand what those differences are in order to correctly analyze and use the data. This paper explains terms and procedures involved in the reference-reach survey that may be misunderstood. This paper also suggests simple changes to the Rosgen reference-reach survey that will enhance the usability of the results for a broader range of research and practical applications.

Hydrologic Design of Bridges and Culverts: A Historical Review

In the 19 th and early 20 th centuries, American civil engineers sized bridges and culverts by empirical methods based on the observed performance of existing structures during floods. Most of these early methods provided a direct estimate of the required waterway area rather than a design discharge. No particular recurrence intervals were associated with the designs. The shortcomings of these early design methods stemmed more from a shortage of useful hydrologic data than from an inadequate understanding of the relevant factors. The first reliable rainfall frequency maps for durations shorter than 24 hours were published in 1935. Advances in frequency analysis in the 1940s led to the development of regional flood-frequency methods for ungaged streams. The 1950s marked the transition to modern frequencybased hydrologic methods in design practice. U.S. PRACTICE IN THE 19 th AND EARLY 20 th CENTURIES

Hydraulic Design of a Lazy River

Lazy rivers are popular attractions at modern aquatic centers and water parks. These recreational water channels carry patrons on floating tubes around a meandering loop. The current is maintained by pumps that withdraw a small fraction of the flow from the channel through large bottom grates and return it to the channel in jets directed downstream. This paper presents the hydraulic relationships needed for lazy-river design. These relationships account for the propulsion of the flow by the water jets and the resistance to flow resulting from friction, bends and drag forces on standing persons. The total pump output power is minimized when the downstream component of the jet velocity equals twice the desired current speed. However, other practical considerations generally favor a higher jet speed. Field tests on three lazy rivers indicate that a Manning n value of 0.015 is sufficient to account for boundary friction, bend losses and other local losses. Persons standing in the flow cause added drag, which can reduce the current speed substantially. A design example illustrates the practical application of the relationships and experimental findings. The investigations presented in this paper were conducted for Water’s Edge Aquatic Design LLC of Lenexa, Kansas. Water’s Edge Aquatic Design is a leading design firm specializing in aquatic centers and water parks. The relationships in this paper have been applied successfully to numerous lazy-river design projects.