UDFCD Guidelines for FHAD Mapping for use in DFIRMS Revision 2b Dated: March 19, 2002 Prepared by: Guidelines for FHAD Mapping for use in DFIRMS Because of the variety of commercially available mapping and/or survey software packages and their varying formats, FEMA applications of Study Contractor (SC) digitally prepared mapping and survey data should be a significant consideration when "collecting" the information. To ensure transportability of graphics and database files from one platform to another, mapping features must be digitally captured into a schema (layer/level or attribute structure) and must be capable of being translated into a common spatial data exchange format. The transportability of digital data should be of prime consideration during the planning phase of a project. Also of concern is the data structure itself. Digital data must be arranged or segregated in such a manner that features are separated onto topical layers/levels or by attributes that conform to the user's needs. This will eliminate the need for later efforts to separate the graphic elements for further work. Complete documentation of file names, sizes, and contents is required. Base mapping and the map projection requirements are the mapper’s responsibility. The engineer is responsible for flood mapping, the project data document, and meeting CAD standards. Map Projection A major aspect of transportability of mapping or survey files to a geographic information system (GIS) is horizontal and vertical positioning on the earth. Mapping data must be controlled to a grid or geographic projection and referenced to horizontal and vertical datums. These positional references are established prior to the surveying process. Survey control is expressed in the form of horizontal and vertical position plotted on a geographic projection or control grid (State Plane). All planimetric and topographic features must be collected/compiled and referenced to this survey control. The FHAD maps shall be delivered in Colorado State Plane, and the appropriate zone projection, with a NAD83 horizontal datum, adjusted to ground (district specified elevation) and NAVD88 vertical datum. Either the conversion factor from ground coordinates to State Plane or a table showing the XY values for several known points in both grid and ground coordinates shall be included in the submittal. The amount of X and Y shift is also acceptable. This information is generally available from the organization providing the base data. This will allow the study area to be used with local government base data. Data Requirements Base mapping must show all current pertinent cultural features, streets with correct names, railroads, airfields, etc. All streets and roads within or near the floodplain shall be shown and named. The plan drawings must show 100-year floodplain boundaries, base flood elevations (BFEs), flood insurance rate zones, floodway boundaries, cross-section lines and their labels, levees, dikes, dams and any other pertinent planimetric features located in, or directly adjacent to, the flood hazard areas; the names of these items should be provided on the map. Hydrographic features such as streams, rivers, canals and flood control structures shall be shown and named. Linestyles (patterns, dashes, etc.) should be applied, not drawn in. Annotation and leader lines must be on separate layers from geographic data. All data should be included in a single drawing file. Flood profiles, map frames, legends, north arrows, etc. should not be included in the single DFIRM drawing. Layers in the drawing should not be split based on the sheets the data came from. A sample CAD file should be reviewed and approved by the District to ensure that data is correctly layered and formatted before the final FHAD is submitted. Units for all distances and elevations must be in feet. The following information is required in a FHAD intended for use as part of a FIRM: Project Data Document This file lists the complete community name, drainageway names, the limits of the detailed study, the flood frequencies analyzed (100-year, 500-year, etc.), and the lowest cross section number for each stream analyzed. It should include the study contractors’ company name and contact information. It must also list the hydraulic model and hydrologic model used in the analysis and the study date. This document will include the cross-sections table described below. It will also state the predominant feature types depicted: variations must be noted individually on the drawing. Base Flood Elevations (BFEs) BFEs represent 100-year flood elevations and are shown by contours drawn normal to the direction of the flow of floodwater; they should extend completely across the 100-year floodplain. The BFE lines must each be represented as a continuous line with the minimum number of vertices to correctly represent the feature. Each contour should indicate its elevation above NGVD datum, measured to the nearest whole foot. BFE lines must include supporting information stating their elevation. Cross Sections The locations of all cross sections used in the hydraulic model should be shown. The lines drawn should correspond to the actual sections studied and should cross the largest floodplain studied (i.e., 500-year floodplain). Locations of cross section lines on the work map must correspond to the cross section locations on the flood profiles. Distances between cross sections, as measured along the stream channel or hydraulic base line, must agree with corresponding distances shown on the flood profiles to within a maximum tolerance of 5 percent of the map scale. This tolerance applies to deliverable materials, not to information maintained in supporting files. Cross sections must include supporting information stating the cross-section number. A table must be included in electronic format, containing additional information about the cross section. The table must include the cross-section number, the name of the stream it crosses (if there are multiple streams in the study), the base flood elevation at that cross section, and the measurement along the stream to the cross section location. This information is generally recorded in the Floodway Data table. Flood Hazard Areas All 100-year flood zones should be shown, including areas of shallow flooding. Each zone should be on a separate layer. Each zone should be made up of closed polyline features, and adjacent zones will have coincident boundaries. Flood zones do not include portions of other zones (for instance, 500-year zones do not include any of the 100-year zones) Supporting information includes the type of floodway (floodway or easement) and whether the zone is a special flood hazard area (SFHA). Areas of shallow flooding should be given either a static BFE or an approximate depth in feet. This information can be in the form of text on a separate layer in the drawing or can be added as block attributes in AutoCad Map. The contractor must merge together areas where a tributary flows into the main channel in an appropriate manner. Include the limits of each study. Do not allow gaps in the data due to sheet size or small gaps between studies. General Structures All structures with hydrologic impacts should be shown according to their effects. Spatial elements representing general structures are represented by lines. The lines should represent the primary characteristic of the structure. For example, bridges should be represented by the transportation centerline carried by the bridge. Dams should be represented by a line corresponding to the top of the dam. Levees should be represented by a line corresponding to the top of levee. A line corresponding to the centerline of the main barrel should represent a culvert. FEMA divides general structures into: • aqueduct, bridge, channel, channel contains 1% flood, channel contains 0.2% flood, floodway contained in channel, culvert, culvert contains 1% flood, culvert contains 0.2% flood, dam, dike, dock, fish ladder, footbridge, flume, gate, jetty, levee, lock, penstock, pier, seawall, weir, wing wall If a structure does not fit into one of these categories but its impact is similar to one of them it should be included in that layer. For example, drop structures are hydrologically similar to weirs, so they should be included on the weir layer. Hydrography Each existing hydrographic feature should be completely shown on the Hydro layer, together with information about its name (if applicable), and the type of feature. The set of feature types FEMA uses is: • channel, ditch, glacier, gulch, hatchery, perennial river/stream, intermittent river/stream, profile baseline, water separation line, wash, shoreline/coastline, lake, reservoir, race, waterfall, tailings pond, bog, swamp, retention pond Layer Schema Requirements Only applicable layers should be created. DESCRIPTION LAYER NAME Flooding Elements Floodway Boundary floodway 1% Flood Hazard 100-year 1% Shallow Flooding 100-shallow 0.2% Flood Hazard 500-year BFE bfe Cross Section xsection Limit of Floodway limitfldway Limit of Study limitstudy Limit of Detailed Study lods End of Spatial Extent endspatial Apparent Limit applimit 1% Shallow Flooding Hatch hatch100 BFE Text bfetxt Cross Section Text xsectxt Cross Section Hexagon xsec-hex Limit of Flooding Text limittxt Flood Zone Text zonetxt Hydro Elements Hydrologic Features hydro Water Feature Text draintxt Landform/Island Text islandtxt 1000 Foot Marker & Text rivermk River Mile Marker & Text rivermk Structure Elements Weir weir Dam dam Levee levee Channel channel Channel Contains 1% Flood channel_100 Channel Contains 0.2% Flood channel_500 Culvert culvert Culvert Contains 1% Flood culvert_100 Culvert Contains 0.2% Flood culvert_500 Bridge bridge Footbridge footbridge Other structures other_struct Structure Text structxt Base Map Elements Roads road Railroads railroad Buildings building Road Text roadtxt Layers with Required Annotation – may omit annotation for areas of default values Feature Data Required Annotation Text Layer Layer BFE One line for each Base Flood • Elevation BfeTxt Elevation XSection One line for each cross- • Cross-Section Number XSectTxt section used and/or Letter 100-year Closed polygon representing • Zone ZoneTxt a contiguous flood hazard • Floodway (floodway, area easement) • SFHA 100-shallow Closed polygon representing • Zone ZoneTxt a contiguous flood hazard • Depth for shallow flooding area OR Static BFE • Floodway (floodway, easement) 500-year Closed polygon representing • Zone ZoneTxt a contiguous flood hazard • Floodway (floodway, area easement) Hydro All existing hydrographic • Feature Name DrainTxt features. Streams may be • Feature Type (separate by shown as channel edges or color if multiple types) – as a single line (which note: feature type may be represents thalweg or flow described in project data path) document instead Other_struct Line representing centerline • Type of structure (separate StructTxt of structure by color if multiple types) Allowed Values for Required Annotation Layer : Attribute Allowed Values Default Value ZoneTxt: Zone A, AE, AH, AO, AR, 100 Year Contained in Channel, 100 AE Year Future Conditions, A99, V, VE, 500 Year, 500 Year Contained in Channel, Area Not Included, D, X Protected by Levee, X, Open Water ZoneTxt: Depth Depth of shallow flooding in feet 1 ZoneTxt: Floodway floodway, easement (designated flood-control right-of- floodway way) Zone_Text: SFHA yes, no (is this a special flood hazard area, defined as yes 100-year flood zone with BFEs or velocity determined) DrainTxt: Feature channel, ditch, glacier, gulch, hatchery, perennial channel Type river/stream, intermittent river/stream, profile baseline, water separation line, wash, shoreline/coastline, lake, reservoir, race, waterfall, tailings pond, bog, swamp, retention pond StructTxt : Type aqueduct, floodway contained in channel, dike, dock, fish none ladder, flume, gate, jetty, lock, penstock, pier, seawall, wing wall * Note: Only the values listed above are allowed by FEMA CAD Standards Each layer should be complete without reference to any other layer. For instance, rivers should not have holes in them where a bridge crosses over. Flood zones should close on either side of a structure that contains the flood event, or continue past one that does not contain the flood. Data on required layers should not be created as a block. Point features (such as reference points and stream stationing) may be represented however the contractor wishes, so long as there is also a point representation at the insertion point. Quality control procedures should insure there are no gaps between panel match lines or within a layer, and that all data is on the correct layer. All features must be snapped at match lines and area features must be closed. Combining map sheets into a single CAD file with features continuing across map sheets is required, and will help improve data consistency. Area features such as flood zones must be drawn as discrete closed polygons. If multiple features or feature classes are adjacent, they will have coincident boundaries. The different flood zone layers should not have overlap between them. For instance, a 500- year flood zone will not include areas in the 100-year flood zone. Linestyles (patterns, dashes, etc.) should be applied, not drawn in. Annotation and leader lines must be on separate layers from geographic data. All data must be included in a single drawing file. It should be physically included, not x-refed or associated from another file. Flood profiles, map frames, legends, north arrows, etc. should not be included in the single DFIRM drawing. Layers in the drawing should not be divided based on the sheets the data came from. Annotation All appropriate annotation should be on a corresponding text layer (i.e., DataLayer_Anno) to the feature layer that it is a reference to. Hatching and Text Boundaries Hatching and lines around annotation must not be shown on the same layers with data. Instead, put the hatch in layers named DataLayer_Hatch, and put leader lines and annotation boundaries in layers named DataLayer_Anno Data Format CADD drawings should be provided in AutoCAD R13 format as .DXF files. ARC/INFO .E00 files are also acceptable. Information or annotation about spatial features can be presented in one of four ways: 1. Users of AutoCAD Map can input information by creating one table per layer in object data and adding data for each individual feature. 2. Put ID values directly on each feature as annotation. Then, create a spreadsheet or text table for each feature layer listing the ID and associated information. Again, layering should reflect data layering, but not be part of it. The ID layers can be turned off for plotting purposes. 3. In standard AutoCAD, add a block with data about each piece of required information next to each feature. Blocks should be layered out similarly to the related data, but in separate layers from it. The block should be as close to the feature as possible to avoid confusion in conversion to DFIRMS. The block data need not be visible in the plotted output. 4. ARC/INFO users can add attributes to a series of fields in each coverage. Display Standards Information required in the bottom margin area of each plot (except the single-sheet DFIRM drawing) includes the following: • Date of compilation (month and year) • State Plane, NAD83 • North arrow • Scale • Study Contractor's name • Sheet number (sheet or drawing number should be consistent with index map and AutoCad file naming) • Community Name (Include State/territory) and Study Name may also be included Which data attributes are printed as annotation for each feature is largely at the discretion of the study contractor. For color plots, in order to establish some uniformity, certain basic categories of features should be plotted in specific colors as follows: • Political boundaries-Black • Cross sections-Black • BFEs-Green • Floodplain and floodway boundary information-Red • Hydrography-Blue This color scheme is recommended by FEMA but is not required. Line styles, color schemes, and hatch patterns are changed by FEMA for the final DFIRM product. File Naming File names must be no more than 8 characters long, and should end with the panel number from the map index. The single-sheet DFIRM drawing should include DFIRM in its name.