but which will partially open to allow full access for water and entrained material when the rate of flow is sufficiently high while still obstructing the flow of heavier materials application_number US 7064508 A description referring to fig1 and 2 the gate system 100 of the invention comprises two side brackets 120 and 140 which when attached to a lower fixed screen 160 and upper screen section 180 comprise a frame to which upper gate 200 and rotatable means 230 are affixed side brackets 120 and 140 are 1 u00bc u2033 angle iron braces of sufficient length to span the vertical distance between the street gutter and the top of the standard sewer drain opening in this preferred embodiment side brackets 120 and 140 are constructed of 0 125 u2033 304 stainless steel side brackets 120 and 140 are opposingly affixed to lower gate screen 160 by means of standard cap screws 165 lower gate screen 160 is sized to span the horizontal distance between the left and right sides of a sewer drain opening such that when gate system 100 is installed lower gate 160 effectively blocks debris and other solid matter entering the sewer drain opening at the gutter level in this preferred embodiment lower gate 160 is constructed of 10 gauge 0 75 inch expanded metal stainless steel also shown in fig1 and 2 are anchor plates 145 affixed to both side brackets 120 and 140 and which are used to anchor gate system 100 the opening to the subsurface catch basin positioned above lower gate screen 160 and spanning between side brackets 120 and 140.