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of the building. When restructuring topography, exposed cut and fill slopes, as well as borrow and stockpile areas areas, should be protected Runoff should be diverted from the face of slopes, and slopes should be stabilized with ground cover or retaining walls. C/n:;ulation and Access: Every site must connect with a road system for access to the surrounding infrastru<:ture, and larger development projects require circulation within the site The objective in site design is to meet the program needs for circulation and access while main- taining safe access during flooding and avoiding damage to natural features that aid in the control of runoff and flooding Roads should be minimized to reduce the amount of surface paving Site layout should locate roads to ap- proach buildings from the direction away from the flood- plain so that access routes "ill be less likely to be blocked by the flow of flood waters and debris. This ap- proach will protect natural features in the floodplain and will minimize obstruction of the floodway. To reduce potential erosion, siltation, and runoff problems, roads should not disrupt drainage patterns, and road crossings should be perpendicular to streams, with adequate bridge openings and culverts to permit the unimpeded flow of water If roads are to be raised, the slope of em- bankments should be minimized and open faces stabil- ized "ith ground cover or terracing. eolltrot of StOl'1ll Water RUlIoff Water enters a given site either from precipitation or as runoff from upstream portions of the watershed What happens to this water is a major determinant of both the degree of flooding and the potential of damage from flood- ing I( through development of a site, there is an increase in the volume or velocity of storm water runoff there will be an increase in flooding levels Thus, as an ideal, runoff rates after development should not exceed the rates before devel- opment This ideal may not always be possible or practical and may not be required by regulations, but should remain the objective of good site planning and design Site design techniques should work to protect the in- dividual site, as well as minimizing increased flood levels elsewhere There are a number of key factors that influ- ence storm water runoff and the combination of these must be considered in the site design process. Soils Soil porosity is one component in controlling water runoff. Soil composition needs to be firm enough to adequately support buildings but at the same time per- meable enough to allow percolation of water to recharge the wdter table and to allow water to drain away from buildings. Balanced soil composition slows water runof( increases infiltration, and helps prevent the build-up of Streets should be located to approach buildings from tbe direc#on away from the floodplain so that access is less likely to be hlocked and vehicles are not dam- aged by flood water. Road crossings should be per- pendicular to streams, with adeqw::lte culverts or bridge openings to permit unim- peded flow of water. I----~---:------ :~~ j. w. I~ :*"'.;t~.~U~l2: ii,:J c= [1 I...... " -:-: ....,....,.., lfi)/....:.<:..:......:.. . . ... " ........ ,B ~ L ~ ___ ~ I ---------------" ill I!i Section AA SectIon BB 59