Description: ABOUT THIS DATA:These polygons represent areas that may be susceptible to debris flows, especially during extreme precipitation events. New and existing structures, roadways, bridges, utilities, and other infrastructure located within these mapped debris-flow susceptible areas may be at risk of structural damage and/or sediment inundation. For new/proposed development within these areas, site-specific geologic hazard reports should be required prior to approval of land subdivision or the issuance of building permits. These reports should discuss the degree, limits, and potential impacts of the hazard to the proposed development or land use changes; proper debris-flow mitigation techniques; and feasibility of any recommended mitigation techniques.These polygons were compiled from various CGS Open-File Reports. Please refer to the original Open-File Report for additional information regarding mapping methodology and limitations of use.LIMITATIONS:These polygons depict generalized areas that may be susceptible to debris flows based on available GIS data and limited field observations in easily accessible areas. The polygons were generated at a scale of approximately 1:24,000 (1 inch = approx. 0.4 mi.) and are not valid if enlarged to scales greater than 1:24,000.The degree of susceptibility to a particular geologic hazard, in any given area, is related to ever-changing natural and human-induced conditions, and any alteration in the natural landscape may increase or decrease susceptibility to a particular hazard. The polygons are not intended to assign risk, or indicate the degree, severity, recurrence interval, or exact boundary of individual debris flows or debris-flow susceptible areas.Because of limitations associated with the mapping scale and the scope of this project, some areas that may be susceptible to potentially damaging but localized debris flows near the mouths of small gullies or at the base of steep slopes may not be included. Additionally, some higher-order streams in larger mountain valleys that have been mapped as debris flow susceptibility areas may be more likely to produce water floods than debris flows depending on local rainfall-runoff conditions and availability of erodible sediment and debris in the basin. Inclusion of existing structures and infrastructure within a mapped susceptibility area does not necessarily indicate that debris-flow impacts will occur, in only indicates that these features may be more exposed to debris-flow events than similar features located in other areas. This map should not be used in place of a detailed site-specific geologic hazard study.
Copyright Text: Polygons compiled by Kevin M. McCoy from various CGS Open-File Reports. Last updated December 14, 2018.
Description: The TIGER/Line shapefiles and related database files (.dbf) are an extract of selected geographic and cartographic information from the U.S. Census Bureau's Master Address File / Topologically Integrated Geographic Encoding and Referencing (MAF/TIGER) Database (MTDB). The MTDB represents a seamless national file with no overlaps or gaps between parts, however, each TIGER/Line shapefile is designed to stand alone as an independent data set, or they can be combined to cover the entire nation. The primary legal divisions of most states are termed counties. In Louisiana, these divisions are known as parishes. In Alaska, which has no counties, the equivalent entities are the organized boroughs, city and boroughs, municipalities, and for the unorganized area, census areas. The latter are delineated cooperatively for statistical purposes by the State of Alaska and the Census Bureau. In four states (Maryland, Missouri, Nevada, and Virginia), there are one or more incorporated places that are independent of any county organization and thus constitute primary divisions of their states. These incorporated places are known as independent cities and are treated as equivalent entities for purposes of data presentation. The District of Columbia and Guam have no primary divisions, and each area is considered an equivalent entity for purposes of data presentation. The Census Bureau treats the following entities as equivalents of counties for purposes of data presentation: Municipios in Puerto Rico, Districts and Islands in American Samoa, Municipalities in the Commonwealth of the Northern Mariana Islands, and Islands in the U.S. Virgin Islands. The entire area of the United States, Puerto Rico, and the Island Areas is covered by counties or equivalent entities. The boundaries for counties and equivalent entities are as of January 1, 2017, primarily as reported through the Census Bureau's Boundary and Annexation Survey (BAS).