Laserfiche WebLink
do <br /> <br />recognizes that the management of stormwater runoff to minimize <br />or control downstream channel and bank erosion is a developing <br />technology. Innovative techniques and ideas will be considered <br />and may be used when shown to have the potential to produce <br />successful results. Some alternatives are to: <br /> <br />Avoid increases in surface runoff volume and velocity by <br />including measures to promote infiltration to compensate <br />for increased runoff from areas rendered impervious. <br /> <br />Avoid increases in stormwater discharge velocities by using <br />vegetated or roughened swales and waterways in lieu of <br />closed drains and high ve~locity paved sections. <br /> <br />Provide energy dissipaters at outlets of storssL drainage <br />facilities to reduce flow velocities to the point of discharge. <br />These may range from simple rip-rapped sections to <br />complex structures. <br /> <br />Protect watercourses subject to accelerated erosion by <br />improving cross sections and/or providing erosion-resistant <br />lining. <br /> <br />Exceptions - this rule shall not apply where it can be demonstrated <br />that stormwater discharge velocities will not create an erosion <br />problem in the receiving watercourse. <br /> <br />The following is a table for maximum pe~-missible velocity for <br />stoLmwater discharges: <br /> <br />Maximum Per~tdssible Velocities <br /> <br /> Feet/ Meters/ <br />Material Second Second <br /> <br />Fine sand (noncolloidal) 2.5 <br />Sandy loam (noncolloidal) 2.5 <br />Silt loam (noncolloidal) 3.0 <br />Ordinary fixm loam 3.5 <br />Fine gravel 5.0 <br />Stiff clay (very colloidal) 5.0 <br />Graded, loam to cobbles (noncolloidal) 5.0 <br />Graded, silt to cobbles (colloidal) 5.5 <br />Alluvial silts (noncolloidal) 3.5 <br />Alluvial silts (colloidal) 5~0 <br /> <br />0.8 <br />0.8 <br />0.9 <br />1.1 <br />1.5 <br />1.5 <br />1.5 <br />1.7 <br />1.1 <br />1.5 <br /> <br />12 <br /> <br /> <br />