FLOOD03407

• County: Statewide
• Community: State of Colorado
• Basin: Statewide
• Title: Stormwater Management in the United States - A Study of Intsitutionl Problems, Solutions and Impacts
• Date: 9/1/1980
• Prepared By: Office of Water Research and Technology
• Floodplain - Doc Type: Educational/Technical/Reference Information

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PERSPECTIVES
OF URBAN AND METROPOLITAN STORMWATER MANAGEMENT

5

Introduction

The basic goals of most stormwater management agencies in urban and metropolitan
areas are similar--namely, to solve existing runoff control problems and prevent
new problems from developing. In some places the goals extend beyond this, and many
agencies have much broader horizons of interest and responsibility, The next chap-
ter on stormwater management agencies identifies the multiple responsibilities and
activities of sanitary districts, special districts, and departments of local
governments having stormwater management responsibilities. Other major programs
that these same agencies manage are also identified, such as: wastewater treatment
and disposal, protection and development of water supplies (surface, groundwater),
and multiple-purpose programs extending to recreation, conservation and protection
of natural resources, wildlife protection, general enhancement of the urban en-
vironment, and navigation.

Because the responsibilities and authority of stormwater management agencies are
so diverse, their goals, objective.s, needs and institutional problems are different,
both in type and degree. From the information given in the next chapter, the readers
of this report can develop their own evaluations and comparisons of the agencies
described and the factors that account for the differences and similarities in
agency structure and operation. The purpose of this chapter is to present the
author's perspective of stormwater management, as well as perspectives of profes-
sionals employed by various agencies across the United States that have responsi-
bilities in this field. These viewpoints should help orient readers to the subject,
and provide the basis for understanding and appreciating the opinions, conclusions
and recommendations made in other chapters of this report.

Stormwater: Where It Goes

Most of the precipitation reaching natural, undisturbed land surfaces is stored
temporarily by the soil and vegetation in the area where the rainfall or snowfall
occurs. Only a fraction travels over land surfaces directly to streams, rivers,
and other water bodies. As stormwater percolates through soils, it either; moves
downward to replenish groundwater supplies; moves laterally into nearby streams,
lakes or oceans; or returns to the atmosphere by means of evaporation or trans-
piration through trees and other vegetation.

Effects of Soils, Topography and Land Cover

Exposed, glaciated surface soils allow a moderate amount of infiltration of
stormwater; and, because glacial tills are inorganic in character, little water
remains entrapped in these soils. In areas where heavy, organic soils are found,
water is trapped in the soil, even during lengthy dry periods. When desired, under-
drains can be used effectively in such soils to move the water from "soil storage"
to the receiving water bodies. In highly developed sections of urban and metro-
politan areas, man has replaced exposed soil surfaces with impervious materials
that block direct entry of water into the local soils. Thirty-five percent, or
lIIore, of residential land surfaces may thereby be converted from "highly pervious"
to "impervious". In commercial and industrial developments, this ratio may approach

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