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Water runoff should be routed away .from tbe buildings founda#on be- fore heing allowed to per- colate into the subsoil and water table. .75 ~~ ~r ~~ < I ~~~ Ikr II \11 1111 60 ~______-o , .------.... Vegetation is useful in con- trolling runoff and stabiliz- ing slopes. Foliage and roots hold water and pre- vent erosion. Plant leaves vary in their ability to hold water. Horizontal braru:h- ing is most effective in pre- ven#ng water runoff down the tree truck and erosion at tbe base of tbe tree. Rough bark holds and slows water running down the tree trunk and prevents erosion at the base of tbe tree. extreme water pressure on foundation walls, footings, and floors. The type of soil on the site dictates the appropriate response for site development Soils that remain saturated with water tend to corrode foundations. Heavy clay soils require the addition of sand to improve their drainage, the provision of good surface drainage, or a bed of gravel berween soil and foundation to prevent foundation corro- sion Sand and silt, though porous, are unsuitable for stable foundations. They necessitate pilings to anchor the structure to deeper bearing soil Vegetation. Vegetation aids in slowing the rate of storm water runoff by holding water, both internally and externally, thus allowing it to filter into the ground or evaporate gradually. In addition, vegetation makes an im- portant contribution by helping to prevent erosion and sedimentation that exacerbate flooding Attention should focus on retaining natural vegeta- tion wherever practicable, and on introducing planting in locations that will be most affected by runoff The selec- tion of plants should emphasize compatibility with natu- ral conditions and the ability to hold the maximum amount of water Leaf type, branching characteristics, and the texture of bark all affect water-holding capacity. A fibrous root structure can help control erosion Dune Stabilization. Protection of the dune structure is a vital part of flood damage reduction in coastal areas. Dunes should be preserved in order to fulfill their role in maintaining the balance of the coastal ecosystem In addition to keeping all buildings off dunes, natural vege- tation should be retained to stabilize the dunes' sandy composition Dunes should not be cut or breached by site development features such as walkways. The construction of jetties, groins, and similar structures should likewise be carefully controlled to prevent disturbance of the