8.0 PRSR 03-09-2017 - Laserfiche WebLink

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WATER RESOURCES Surface Waters—Rivers The Elk and Mississippi rivers are the obvious surface water resources in this area. The Orono Dam controls water flow rates in this lower stretch of the Elk River. Following large rain events, especially in the spring,flows can be quite high,though the river rarely floods. Since the river does not flood often,the floodplain tends to be quite narrow,and it tightly follows the course of the river. Flood resistant vegetation reflect this narrow band,with floodplain species occurring in a small band along the river channel.Therefore,prairie vegetation would broadly occupy the uplands,and come very near the river valley.Along the southern edge of the property and along the Mississippi,the situation is somewhat different.The floodplain forest is wider here and is influenced by the greater fluctuations in flow of the Mississippi River. Floodplain In 1965,an historic flood occurred throughout the state.The city of Elk River suspended classes so that male students could help sandbag local establishments and other key areas of the city.Water levels from this flood rose to cover a large portion of the Bailey Point property.Today,more than half of the property lies within the floodway and more of the property is located within riverine zones. Boundaries for the 0.2%annual flood risk cover much of the remaining area. Historically,erosion has not been a problem on the property. However,there are some smaller areas where the bank is eroding along the Elk River.These areas are mainly vegetated by non-native grasses, and do not have tree cover to hold the soil in place.Toward the northwest corner of the property,some vegetation management has occurred, and rip rap was installed to stymie any potential erosion. Buffer Areas The floodplain forest surrounding the property acts as a natural buffer for the waterways. In areas where the forest is wider,is should provide very good water quality protection. Here, runoff from the property can settle before entering the river, and the forest in turn buffers the rest of the property from rapid changes in water levels.The buffer width on the south side of the property is wider than the buffers on the east and west edges.Attempting to increase the buffer sizes through re-vegetation would provide many benefits, including erosion reduction and mitigation of runoff into the river. Stormwater Management Issues The property is somewhat affected by runoff from adjacent properties.The Orono dam largely controls the flow of the Elk River along the north and east sides of the property,while the Mississippi borders the property to the east.Thus,most runoff from adjacent land use flows into those two rivers before it can reach the Conservation Area. Natural flooding of the property can and does occur,especially on the southern tip and on the east side of the property. However,there are also residential properties on the north and west sides that supply some runoff to the Friends of the Mississippi River Bailey Point Nature Preserve NRMP 29