Page:America's Highways 1776–1976.djvu/356

 During World War II, the Public Roads Administration became responsible for constructing satellite airfields and found that data on rainfall and runoff were inadequate. Using rainfall simulators provided and operated by the Soil Conservation Service, a series of experiments on overland flow was conducted on paved and grass surfaces. The data analyzed and reported by Public Roads in 1944 enabled engineers to estimate for the first time flows over overland routes. This paper has become a standard reference on the subject.

After World War II greater interest developed in the application of hydraulic engineering principles to highway design. One of the first applications of the overland flow equations was in the design of a storm drain system in Chicago. From this, Tholin and Kiefer developed the “Chicago Hydrograph Method” which involved routing runoff through the drainage system.

The Public Roads Administration developed a highway engineering drainage manual. The manual provided step-by-step instructions, together with numerous nomographs and charts based on research data, to facilitate the solution of hydraulic equations for design of culverts, open channels, and storm drains. The manual was widely used in draft form by the States in their highway programs and on most of the toll roads because it provided uniform and improved drainage design techniques. It was never formally published and has since been superseded by the series of Hydraulic Engineering Circulars published by BPR beginning in 1960. The original manual and the Circulars have been used as text for training courses and design practices throughout the United States and abroad.

Following a series of disastrous floods, the Iowa State Highway Commission began a research project in 1948 at the University of Iowa to investigate scour around bridge piers. Scour is the severe erosion of firm supporting soils around bridge piers and is the principal factor in the failure of bridges. The results of that investigation enabled bridge designers to estimate the probable depth of scour during floods and provide adequate supports.

A formal hydraulics research program was instituted by Public Roads in 1949 in recognition of the need for systematic study of hydraulics and hydrology as an integral part of highway engineering. The agency conducted in-house research principally in the field of hydrology (analyses of runoff data); supervised contract research at a number of university and Government laboratories; and monitored research undertaken in several States.

In the 1950’s major research was continued on bridge scour at the University of Iowa; culvert design was studied at the National Bureau of Standards; backwater caused by bridges was studied at Colorado State University; head, or energy, losses in storm drain junctions were studied at the University of Missouri; resistance losses in concrete pipe were studied at the University of Minnesota; and urban stormwater runoff was studied at the Johns Hopkins University. All of the research was undertaken as a result of expressed needs evolving from field experience. All reports provided design data and methods readily used by highway designers.

Another field of research begun in the 1950’s in a few States was the Cooperative Highway Program of the U.S. Geological Survey for measurement and analysis of runoff from small watersheds, preferably for at least 10 years in each State. The objective was to estimate the magnitude and frequency of peak flows from watersheds generally under 25 square miles in area. The program has grown to include at present about 30 States with an annual total expenditure of about $1 million.

To protect this cut slope from erosion during highway construction, the first section of the cut already has new grass growing. The second section has been seeded and mulched, while earthwork is still in progress on the third section. 350