the hydrology that previously occurred. Potential sources of informa- 

 tion include: 



a. Stream or tidal gage data. If a stream or tidal gaging station 

 is located near the area, it may be possible to calculate 

 elevations representing the upper limit of wetlands hydrology 

 based on duration of inundation. Consult hydrologists from the 

 local CE District Office for assistance. The resulting mean 

 sea level elevation will represent the upper limit of inunda- 

 tion for the area in the absence of any alteration. If fill 

 material has not been placed on the area, survey this elevation 

 from the nearest USGS benchmark. Record elevations represent- 

 ing zone boundaries on DATA FORM 3. If fill material has been 

 placed on the area, compare the calculated elevation with 

 elevations shown on a USGS quadrangle or any other survey map 

 that predated site alteration. 



b. Field hydrologic indicators. Certain field indicators of wet- 

 land hydrology (PART III, paragraph 49) may still be present. 

 Look for watermarks on trees or other structures, drift lines, 

 and debris deposits. Record these on DATA FORM 3. If adjacent 

 undisturbed areas are in the same topographic position and are 

 similarly influenced by the same sources of inundation, look 

 for wetland indicators in these areas. 



c. Aerial photography. Examine any available aerial photography 

 and determine whether the area was inundated at the time of the 

 photographic mission. Consider the time of the year that the 

 aerial photography was taken and use only photography taken 

 during the growing season and prior to site alteration. 



d. Historical records. Examine any available historical records 

 for evidence that the area has been periodically inundated. 

 Obtain copies of any such information and record findings on 

 DATA FORM 3. 



e. Floodplain Management Maps. Determine the previous frequency 

 of inundation of the area from Floodplain Management Maps (if 

 available). Record flood frequency on DATA FORM 3. 



f_. Public or local government officials. Contact individuals who 

 might have knowledge that the area was periodically inundated. 



If sufficient data on hydrology that existed prior to site alteration 

 can be obtained to determine whether wetland hydrology was previously 

 present, PROCEED TO STEP 4. If not, a determination involving hydrol- 

 ogy cannot be made. Use other parameters (Subsections 1 and 2) for the 

 wetland determination. Return to either the appropriate subsection of 

 Section D or to Section E and complete the necessary data forms. 

 PROCEED TO STEP 4 if the previous hydrology can be characterized. 

 • STEP 4 - Determine Whether Wetland Hydrology Previously Occurred. 

 Examine the available data and determine whether indicators of wetland 



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