Anatomy of an urban flood

Abstract

Due to the scarcity of land for development in urban areas, more and more land which was once open space with trees and ground cover is being developed into residential and commercial properties. This phenomenon is having a deleterious effect on existing properties and storm drainage systems. The development is changing the character of urban hydrology. Development is reducing the tree canopy and larger residential and commercial buildings are increasing the percentage of land area impervious to run-off. These two major factors have adversely impacted urban hydrology. They have increased the amount of runoff to be handled by existing storm-water drainage systems and because of this the existing infrastructure has become inadequate to handle normal storm runoff. In the case of unusual rainfall the results are catastrophic. The inability to carry off excessive rainfall results in serious flooding. This paper takes the reader through the thought processes involved in the investigation, analysis and design of alternative solutions for the remediation of an urban flood that resulted in substantial monetary loss (over $50k) and the loss of priceless personal family heir-looms to one urban family. This "Anatomy" of an Urban Flood briefly discusses the many facets involved in arriving at an acceptable engineering solution, including the engineering (hydrologic and hydraulic) considerations, the social, economic, political and legal aspects of the problem. The primary focus of the paper is on an innovative approach to assigning value to the intangibles associated with the problem.