Subsection 3 - Hydrology 



75. Apply the following steps to determine whether wetland hydrology 

 previously occurred: 



• STEP 1 - Describe the Type of Alteration. Examine the area and 

 describe the type of alteration that occurred. Look for evidence of: 



a. Dams . Has recent construction of a dam or some natural event 

 (e.g. beaver activity or landslide) caused the area to become 

 increasingly wetter or drier? NOTE: This activity could have 

 occurred a considerable distance away from the site in 

 question. 



b. Levees, dikes, and similar structures. Have levees or dikes 

 recently been constructed that prevent the area from becoming 

 periodically inundated by overbank flooding? 



£. Ditching. Have ditches been constructed recently that cause 

 the area to drain more rapidly following inundation? 



d. Filling of channels or depressions (land-leveling). Have natu- 

 ral channels or depressions been recently filled? 



£. Diversion of water. Has an upstream drainage pattern been 

 altered that results in water being diverted from the area? 



£. Ground-water extraction. Has prolonged and intensive pumping 

 of ground water for irrigation or other purposes significantly 

 lowered the water table and/or altered drainage patterns? 



£. Channelization. Have feeder streams recently been channelized 

 sufficiently to alter the frequency and/or duration of 

 inundation? 



Determine the approximate date* when the alteration occurred. Record 



observations on DATA FORM 3 and PROCEED TO STEP 2. 



• STEP 2 - Describe Effects of Alteration on Area Hydrology. Record on 

 DATA FORM 3 a general description of how the observed alteration 



(STEP 1) has affected the area. Consider the following: 



a. Is the area more frequently or less frequently inundated than 

 prior to alteration? To what degree and why? 



b. Is the duration of inundation and soil saturation different 

 than prior to alteration? How much different and why? 



PROCEED TO STEP 3. 



• STEP 3 - Characterize the Hydrology That Previously Existed in the 

 Area. Obtain all possible evidence that may be used to characterize 



* It is especially important to determine whether the alteration occurred 

 prior to implementation of Section A04. 



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