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Scope or Services <br />Hanson Pits Channel Migration and Avulsion Risk Assessment <br />Kittitas County Flood Control District (County) is advancing a strategy to identify and pursue <br />funding for projects where the County can decommission obsolete flood control structures and <br />improve geomorphic processes that create and sustain high quality salmon habitat. The <br />Hanson Pits levee and downstream private berm have been identified as structures that may no <br />longer be needed and recent propefty acquisitions landward of these facilities presents an <br />opportunity to remove or modify the structures and restore floodplain function, The County <br />owns the Hanson Pits (as series of old gravel barrow pits) and several large agricultural parcels <br />immediately downstream. The Hanson Pits levee and the private berm are both in poor <br />condition and likely will fail sometime in the future; however, they currently provide limited <br />protection for the properties by preventing the river from avulsing or migrating into them. The <br />County desires to develop and implement a plan that will allow part or all of the Hanson Pits <br />levee and private berm to be decommissioned, the borrow pits and portions of the floodplain to <br />be reconnected to the river and restored for habitat, and continued agricultural activities on the <br />downstream parcels. The County is concerned that removing all or portions of the levee and <br />berm may allow the river to avulse or migrate into the pits and the downstream properties. This <br />risk needs to be understood and incorporated into land use planning. Channel migration may be <br />okay, so long as ecologic function associated with wetland, riparian, and instream habitat is not <br />degraded and agricultural activities can continue on portions of the downstream properties. <br />The County has requested Watershed Science & Engineering (Consultant) to conduct an <br />avulsion / channel migration risk investigation to predict how the river may respond to various <br />levee/berm decommissioning alternatives for the purpose of helping the County make an <br />informed decision as to how best to proceed with the decommissioning / restoration project. <br />The scope of the WSE investigation is described in the tasks below. <br />TASKS <br />1. Data Gollection and Review <br />The consultant shall collect and review existing data needed to complete the avulsion / channel <br />migration investigation. lnformation will include but not be limited to: