Modeling an Urban Development with MIKE-SWMM Presented by: Melissa Figurski

Site Layout acres 46.8% Impervious

Design Approaches Who cares about the environment anyway… Earth Day is every day…

MIKE-SWMM Evaluations Pre-development –Natural runoff Post-development –Sewer system pipe runoff –Grassy swale to detention pond runoff

Design Criteria, City of Austin Drainage Criteria Manual – detention ponds “Ponds shall be designed to reduce post- development peak rates of discharge to existing pre- development peak rates of discharge from the 2, 10, and 25 year storm events at each point of discharge from the project or development site.” Environmental Criteria Manual – runoff treatment volume “one-half inch of runoff plus an additional one-tenth inch for each ten percent increase of gross impervious cover over twenty percent within the drainage area to the control”

Design Storms for Austin, Texas Technical Paper 40 Used SCS Type-II Distribution 2 year, 24-hour Storm 4.1 inches 10 year, 24-hour Storm 6.7 inches 25 year, 24-hour Storm 7.8 inches

Undeveloped Site 10-year storm

Site Layout acres 46.8% Impervious

Developed Site – Obtaining Watershed Parameters Does anyone know how to use this thing?!?!

Developed Site – Obtaining Watershed Parameters

Drainage Schematic For Pipe Flow

RUNOFF Block

EXTRAN Block

Developed Site – concrete drainage with no controls Gutters cannot carry the 10 year storm

Developed Site – concrete drainage with no controls 146 cfs!!

Developed Site – Grass Drainage

78.9 cfs - Getting Better… but there’s more work to be done!

MIKE-VIEW

Pond Sizing

Sum Outflow Hydrographs

Pond Sizing 41.3 cfs 10-year Storm Storage = 126,134.8 ft 3 2-year Storm Storage = 77, ft 3

Pond Sizing Stage-Storage Table 10-year Control 2-year Control WQ Control Pond Outfall

Almost There… Input Pond Stage/Storage Data into MIKE-SWMM Size Pond Outfall Structures for 2 and 10-year Storms Convince World to Use Swales