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<br />VOL. 25, NO. "
<br />
<br />WATER RESOURCES BULLETIN
<br />AMERICAN WATER RESOURCES ASSOCIATION
<br />
<br />AUGUST 1989
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<br />HUMAN STABILITY IN A mGH FLOOD HAZARD ZONE 1
<br />
<br />S.R. Abt, R.J. Wittler, A. Taylor, and D.J. Love2
<br />
<br />ABSTRACT: The delineation of high flood hazard zoneB within a flood
<br />plain ill usually independent of the hydraulic parameters that con-
<br />stitute a life threatening situation. In order to derme human instabil-
<br />ity in high hazard areas, a study was conducted to identify when an
<br />adult human could not stand or maneuver in a simulated flood flow.
<br />An analysis was performed on a rigid body monolith resulting in a
<br />toppling hazard envelope curve (velocity VB. depth). A 120 lb monolith
<br />was then constructed and tested to relate the actual flow velocity and
<br />depth at toppling to theory. A BerieB of human BubjectB (90.201lbs)
<br />were placed in a recirculating flume and tested to determine the ve.
<br />locity and depth of flow that caused their instability.
<br />The test results determined that the product number, which is the
<br />product of the velocity and depth at toppling of the monolith, closely
<br />compared to the theoretical envelope curve. The monolith results rep-
<br />resent the lower limit of human stability. Also, the product number
<br />appeared to be a predictor of human instability in flood flow. A rela-
<br />tionship was developed to estimate the product number at which a
<br />human subject becomes unstable as a function of the height and
<br />weight of the subject.
<br />(KEY TERMS: flood hazard; human Btability; product number.)
<br />
<br />INTRODUCTION
<br />
<br />The concept of a high flood hazard zone has evolved
<br />during the 1970s and 1980s as one means for regulating
<br />development activities in flood plains to minimize prop-
<br />erty damage and loss of human life, However, it is not
<br />clear how a high flood hazard directly relates to the loss
<br />of human life. For example, when does the velocity
<br />and/or depth of flood flow pose a life threatening haz-
<br />ard? It is important to relate the concept of a high flood
<br />hazard to the limits of human survivability,
<br />The definition of a high flood hazard zone is often
<br />vague and varies significantly between regulating
<br />agencies (City of Boulder, 1981). For example, one
<br />Federal entity may define the floodway (high hazard
<br />zone) as that area within the lOO-year flood plain
<br />which, when encroached equally from both boundaries
<br />
<br />of the flood plain, results in a one-foot rise in the 100-
<br />year base flood elevation (Federal Emergency
<br />Management Agency, 1987). A regional entity may de-
<br />fine the floodway as the area within the loo-year flood
<br />plain which, when encroached equally from both
<br />boundaries of the flood plain, results in a half-foot rise
<br />in the 100-year base flood elevation (Urban Drainage
<br />and Flood Control District, 1970). A local flood utility
<br />may define the floodway as; when flow velocities meet
<br />or exceed two feet per second; when flood depth meets
<br />or exceeds two feet in depth; or, when a half-foot rise
<br />encroachment occurs (City of Boulder, Colorado, 1981).
<br />All three floodway definitions present a conservative
<br />approach to identifying a high flood hazard zone but do
<br />not specifically relate the high flood hazard to the upper
<br />limit of human stability in flood flows. Perhaps it may
<br />be possible to link high flood hazard delineation to hu-
<br />man instability in flood flows.
<br />It was the objective of this pilot study to conduct an
<br />analysis and predict the approximate depth and veloc-
<br />ity of flow in which an idealized, rigid body structure
<br />will topple into flood flow, Then, a series of human sub-
<br />jects were tested in a recirculating flume to determine
<br />which depths and velocities of flow result in instability.
<br />A comparison of rigid body and human test results will
<br />be performed using a product number approach where
<br />the product number (P,N.) is defined as
<br />
<br />P,N, = d x V fWsec
<br />
<br />(1)
<br />
<br />as d is the depth of flow in feet and V is the average ve-
<br />locity in feet per second. Criteria will be presented that
<br />may better relate a high flood hazard to the upper limit
<br />of human survivability in flood flow (City of Boulder,
<br />Colorado, 1981). Previous work of this nature was not
<br />located in the literature,
<br />
<br />IpaperNo. 89010 of the Water Resources Bulletin. Discus8ioDll are open until April 1, 1990.
<br />2Respectively, Professor, Department of Civil Engineering, Engineering Research Center, Colorado State University, Fort Collins, Colorado
<br />80523; Staff Hydraulic Engineer, U.S. Bureau of Reclamation, 857 So. Van Gordon Ct., 1205, Lakewood, Colorado 80228; Civil Engioeer,
<br />Department of Public Works, City of Boulder, Utilities Division, P.O. Box 791, Boulder, Colorado 80302; and Principal, Consultant, DavidJ. Love
<br />& Associates, Inc., 2995 Cenlergreen Court, South, Suile C, Boulder, Colorado 80301-5421.
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<br />WATER RESOURCES BULLETIN
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