areas. Recorded data usually provide both short- and long-term information 

 about frequency and duration of inundation, but contain little or no informa- 

 tion about soil saturation, which must be gained from soil surveys or other 

 similar sources. The remaining indicators require field observations. Field 

 indicators are evidence of present or past hydrologic events (e.g. location 

 and height of flooding). Indicators for recorded data and field observations 

 include : * 



a. Recorded data. Stream gage data, lake gage data, tidal gage 

 data, flood predictions, and historical data may be available 

 from the following sources: 



(1) CE District Offices. Most CE Districts maintain stream, 

 lake, and tidal gage records for major water bodies in 

 their area. In addition, CE planning and design documents 

 often contain valuable hydrologic information. For exam- 

 ple, a General Design Memorandum (GDM) usually describes 

 flooding frequencies and durations for a project area. 

 Furthermore, the extent of flooding within a project area 

 is sometimes indicated in the GDM according to elevation 

 (height) of certain flood frequencies (1-, 2-, 5-, 

 10-year, etc. ) . 



(2) US Geological Survey (USGS). Stream and tidal gage data 

 are available from the USGS offices throughout the Nation, 

 and the latter are also available from the National 

 Oceanic and Atmospheric Administration. CE Districts 

 often have such records. 



(3) State, county, and local agencies. These agencies often 

 have responsibility for flood control/relief and flood 

 insurance . 



(4) Soil Conservation Service Small Watershed Projects. Plan- 

 ning documents from this agency are often helpful, and can 

 be obtained from the SCS district office in the county. 



(5) Planning documents of developers. 



b. Field data. The following field hydrologic indicators can be 

 assessed quickly, and although some of them are not necessarily 

 indicative of hydrologic events that occur only during the 

 growing season, they do provide evidence that inundation and/or 

 soil saturation has occurred: 



(1) Visual observation of inundation. The most obvious and 



revealing hydrologic indicator may be simply observing the 

 areal extent of inundation. However, because seasonal 



* Indicators are listed in order of decreasing reliability. Although all are 

 valid indicators, some are stronger indicators than others. When a decision 

 is based on an indicator appearing in the lower portion of the list, 

 re-evaluate the parameter to ensure that the proper decision was reached. 



37 



