1. Basic Hydraulics: Storm Water Management concepts

2. Storm Water Defined in Construction General Permit as Rainfall runoff;
Snow melt runoff;
Surface runoff and drainage.
Defines in the HDM 13-2 as
Overland flow
Flow in ditches
Flow in storm drain

3. Storm Water Management
Structural (ditches, ponds, etc.) and non-structural measures to
Control quantity (how much)
Arrival time (when)
Quality (how dirty)

4. Best Management Practices
Practices to mitigate quantity and quality issues
Processes
Street cleaning
Scheduling
Devices
Detention ponds
Rock filter dams
Vegetative buffer

5. Best Management Practices
Practices to mitigate quantity and quality issues
Processes
Street cleaning
Scheduling
Devices
Detention ponds
Rock filter dams
Vegetative buffer

6. Best Management Practices
Water quality issues tend to dominate design practice.
Practices need not be “devices”
Construction activities
Erosion control

7. Storm Drain Systems
EPA NPDES municipal separate storm sewer systems influence BMP selection
Edwards Aquifer Recharge Zone (TNRCC) also influences BMP selection
Division of Environmental Affairs

8. Erosion Control
Turbidity (cloudiness) and Total Suspended Solids are used as regulated parameters for Storm Water Management – Erosion control greatly influences these parameters

9. Erosion Control Flat side slopes in channels, swales, etc.
Protection at culvert outlets
Berms and similar protective devices
Rock filter dams are temporary sediment controls that can be left in place and eventually become a berm that self-seeds and provided hydraulic detention as well as vegetative buffering
Ground cover selection

10. Erosion Control Select route where erosion is unlikely
Design slopes flatter than required by soil considerations
Reduce area of unprotected soil exposure
Reduce duration of unprotected soil exposure
Protect bare soil with vegetative cover, mulch, erosion resistant materials
Retard (delay) runoff with engineered devices (ponds)

11. Channels and Chutes
Surface channels to carry storm water with minimal erosion – velocities are important
Chutes (steep channels) carry water at high velocity – energy dissipation is vital

12. Quantity (How Much) Management
Storage
Delays arrival at a location
Infiltration
Increases rate of water flow into soil

13. Ditches, curbs, etc.
Drains or inlets appearing in ditches and medians are usually grate inlets and are also termed “drop inlets.”

14. Ditches, curbs, etc.
Curbs are the usual roadway bounding feature in urban areas. They may vary in height from negligible (in cases where a roadway has been repeatedly overlaid), and 8”.
Curbs serve multiple purposes; they provide minor redirection for errant vehicles, as well as serving as a bounding feature for water running in the roadway as an open channel.
Curbs may also provide constraint that allows them to become a part of inlets.

15. Hydraulics as pre–requisite
Generally the hydraulics of storm water management is accomplished by various approaches discussed earlier in the course
There is some added effort in velocity management (to control erosion) and sizing storage facilities