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. . . . . . . . . . . . . . . . . . . . . . I- I. . . . . ,. '. . I- . . , I. '. . - . I- . . 5 02/23/00 Stage I . Is the landform a sedimentary deposit composed of alluvium or debris-flow deposits? (Refer to surficial geologic and soils maps,) Recognizing and . Does the landform have the shape of a fan? Characterizing -- (Refer to topographic maps,) Alluvial Fan . Is the landform located at a topographic break? Landforms (Refer to topographic maps,) . Where are the lateral boundaries of the fan? (Refer to topographic and soils maps, surficial geologic maps, and aerial photographs.) Defming Active and · What parts of the alluvial fan are still active? . What parts are inactive but subject to flooding? Inactive Areas of ----t> (Refer to aerial photographs, topographic and soils Erosion and Deposition maps, surficial geologic maps, and historical records in a preliminary assessment to plan a more detailed field investigation,) . Determine method of analysis (deterministic, probabilistic or geomorphic) based on assumptions, limitations and Defming the 100- recommended applications, Year Flood Within -- . To what extent and degree is alluvial fan flooding the Defmed Areas occurring within the defmed areas? (Refer to recent aerial photographs, topographic and soils maps, historical records, and detailed field mapping to support analysis,) Stage 2 Stage 3 Figure 2 Three Stages of the Process To IdentifY and Map Alluvial Fan Flooding (Original published in National Research Council, 1996, Figure 3-1; amended by FEMA) -