Introduction
From 1948 through 1967 The Johns Hopkins University conducted a Storm Drainage Research Project, the most comprehensive field research project to date.
Over the 1948-1967 period a total of 52 different sewered catchments were gaged.(*)*
Data considered to be among the best accumulated during the project are available for two catchments, Northwo od(2) (19-ha) and Gray Haven^3^ (9-ha). No water quality sampling was performed.
Findings from the first satisfactorily instrumented sewered catchment for ascertaining runoff water quality were reported in 1 9 6 4 ^ ) (Mt. Washington, Cincinnati, Ohio, 12-ha).
A 1964 handbook^-*' noted a serious need for much more extensive urban drainage field research, consistent with the huge public expenditures in these facilities. The major finding soon afterward of the first Engineering Foundation conference co-sponsored by what is now the ASCE Urban Water Resources Research Council was that the acquisition of much more field data was the greatest
research need in urban hydrology.(k'
In 1969, a plan for a nationwide field data acquisition program was published.''' Major features of the proposed plan are shown schematically in Figure 1.(7) Principal benefits that were expected to accrue from an effective national program of urban storm drainage research were: ( 1 ) , national criteria
for more efficient and dependable planning, implementation and operation of
urban storm drainage facilities, on acceptable socio-economic bases; ( 2 ) , national quantification of pollution from urban storm drainage systems; and ( 3 ) , resolution of the only major criteria missing for effective planning, design and operation of quantity and quality exchanges between various urban water service categories.
The "National Data Network" of Figure 1 calls for several installations repre-senting a variety of land uses in each of several representative metropolitan regions, with respect to data acquisition, reduction and reporting. Each
installation would have had synchronous, real-time, central recording of rainfall, runoff and quality data. In each research catchment, flow would be measured and water quality samples would be taken not only at the outfall but at several
junctions of the underground sewer system and at several street inlets; and quality and flow from roofs of sample buildings was to have been determined from time to time. Concurrent instrumentation refinement and mathematical modeling development was strongly recommended. The minimum three-year national effort pro-posed would have cost a total of less than one-third of one per cent of the national investment in construction of storm drainage facilities for only one year.
The U.S. Geological Survey has long been active in urban strearaflow data collection.
(8)
The sewered catchment "Pilot Installations" of Figure 1 have been satisfied and progress on the "National Data Network" of Figure 1 has been made by the USGS in cooperative projects with local governments in Philadelphia (two catch-ments, 1974), Pompano, Florida (three catchcatch-ments, 1974) and Denver (three catchcatch-ments, 1975). The Philadelphia installation is described later in this section. (Also Numbered references are cited at the end of this Section.
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described are: some other advances in instrumentation and data logging; some advances in automatic control; the development of a data bank; a new field project
in Rochester, New York; and progress in water balance inventories).
In Section 2 it was suggested that mathematical model development for sewered system applications has seemingly already greatly outpaced the data base for model verification. Doubt has been expressed that practicing engineers will make any wholesale abandonments of empirical methods in favor of more scientific approaches until more extensive verification of various models has been accomplished.("' These regressive views should not be interpreted as indictments of failure. There have been considerable advances in the state-of-the-art, particularly in modeling, over the past decade. However, as subjectively represented in Figure 2,(*-"' the needs for more and better data are growing faster than such advances are taking place. The changing
"Information Needs" of Figure 2 refer to: rising project complexity; increasing potentials for investments required; and constantly changing "rules of the game", such as by the environmental movement, the 1972 Amendments to the Federal Water Pollution Control Act, the flood insurance acts, more extensive land-use planning, temporisation on policy by enforcement agencies, etc., all of which are interrelated and lead to greater needs for hard information. As things now stand, local govern-ments are substantially on their own for the acquisition of field data and no
integrated or national program exists or is in sight.
Flow Measurement
Inlets. A large part of The Johns Hopkins University p r o j e c t ^ ' effort was devoted to the smaller catchments, particularly those that drained directly to
stormwater inlets.'*•*•' Instrumentation featured synchronous, continuous, automatic recording of rainfall rate and the flow level behind a weir.^ ' Weirs were installed in the underground catch basins of several inlets. Two of the inlet catchments are cited in Table 1 of Section 2. While some instrumentation improvements have since been made, the basic techniques employed still represent the state-of-the-art on inlet
catchment measurements.
In-System„ A means for measuring flow in circular storm sewers has been
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developed by the U.S. Geological Survey.^±J-' The first field installation was in Philadelphia, described in a later subsection. Laboratory test documentation has not yet been published, but an accuracy of Í57» under both open-channel and full-pipe conditions has been claimed for this device.^ •3-' As shown in Figure 3, the device features a U-shaped insert constriction, fabricated of fiberglass in symmetrical half-sections to facilitate transportation and installation. Subcritical and supercritical open-channel flow and pressure flows may be gaged.
Extensive laboratory tests have been conducted on an alternative device which also features a ramped constriction, but the constriction is restricted to
the side of the sewer and does not affect the invert.^ ' There has not yet been an opportunity to field-test this meter.
A detailed review of various potential in-system sewer flow meters was made in 1 9 6 8 . (1 5 )
General. As noted in Section 2, almost all flow gagings have been at sewer outfalls or downstream from outfalls. Catchments gaged at outfalls were identified in 1969'-' and partly sewered gaged catchments were identified in 1970.( °' Many of these catchments are cited in Table 1, Section 2. Features of various existing devices for storm and combined sewer flow measurement have been summarized,(17) based on a new comprehensive catalogue of over 70 different
generic types of primary flow measurement devices.(i ö' Field flow measurements
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