47.5 MB - The Whole Building Design Guide

Table 2-3: Checklist for Building Vulnerability of Flood-Prone Critical Facilities (continued)Vulnerability Sections Guidance ObservationsSite Conditions (continued)What is the expectedvelocity of floodwaters on thesite?Are waves expected to affectthe site?Is there information on howquickly floodwaters mayaffect the site?What is the expectedduration of flooding?Is there a history of floodrelateddebris problems orerosion on the site?Is the site within an areapredicted to flood if alevee or floodwall fails or isovertopped?Is the site in an areapredicted to be inundatedif an upstream dam were tofail?Velocity is a factor in computing loads associatedwith hydrodynamic forces, including drag onbuilding surfaces. Approximations of velocitymay be interpolated from data in the FISFloodway Data Table if the waterway wasstudied using detailed methods, application ofapproximation methods based on continuity,local observations and sources, or site-specificstudies.Waves can exert considerable dynamic forceson buildings and contribute to erosion and scour.Wind-driven waves occur in areas subject tocoastal flooding and where unobstructed windsaffect wide floodplains (large lakes and majorrivers). Standing waves may occur in riverinefloodplains where high velocities are present.Warning time is a key factor in the safe andorderly evacuation of critical facilities. Certainprotective measures may require adequatewarning so that actions can be taken by skilledpersonnel.Duration has bearing on the stability of earthenfills, access to a site and emergency response,and durability of materials that come into contactwith water. Records of actual flooding are thebest indicator of duration as most floodplainanalyses do not examine duration.Site design should account for deposition ofdebris and sediment, as well as the potentialfor erosion-related movement of the shoreline orwaterway. Buildings exposed to debris impactor undermining by scour and erosion should bedesigned to account for these conditions.Flood protection works may be distant from sitesand not readily observable. Although a lowprobability event, failure or overtopping cancause unexpected and catastrophic damagebecause the protected lands are not regulated asflood hazard areas.MAKING CRITICAL FACILITIES SAFE FROM Flooding2-93