Types of Stormwater Inlets from HEC12 and HEC22

Note:  Types of Stormwater Inlets from HEC12 and HEC22

Stormwater Inlets consist of four main types (http://onlinemanuals.txdot.gov/txdotmanuals/hyd/storm_drain_inlets.htm) with most common shown in Figure 1.

1.   Curb opening inlets either at a sag or continuous on the street,
2.   Grate Inlets either at a sag or in combination with a Curb opening
3.   Slotted Drains in parking lots which can be simulated as curb opening inlets and
4.   Combination inlets either at a sag or continuous on the street which combine a curb opening inlet and a grate inlet for the stormwater runoff

A sag inlet is the end of the line for the runoff because the flow and its debris load have no other place to go as described in the HEC-22 and HEC-12 manuals and a continuous grade inlet is designed to capture the entire runoff flow but if the flow is too large or the inlet is clogged the bypassed flow can travel past the inlet and flow on down the street to a new inlet.   The interception of a sag inlet is ultimately 100 percent but the amount of interception by a continous inlet is variable and is governed by the width of the opening, the grade of the street, the splash over velocity and the amount of side and flontal flow in a grated or combination inlet which is governed by the width and the length of the grate.  Any flow in a continous opening inlet that is not captured ends up as bypass flow and travels down the downstream link or conduit (Figure's 2, 3, 4, 5 and 6).

Figure 1.  Common Types of Stormwater Inlets on Streets

Figure 2.  Continuous Grate Inlet(1) and Sag Curb Opening Inlet(4)

 

Figure 3.  Curb Opening Inlets(2)

Figure 4.  Continuous Curb Opening Inlet(2)

Figure 5: Grate Inlets and Combination Inlets (1, 3 and 5)

How to Easily Make a Smaller Model in InfoSWMM Using Trace Upstream Network

How to Easily Make a Smaller Model in InfoSWMM Using Trace Upstream Network

Step 1.  Use the Trace Upstream Network command to find all of the network above the node of interest (Figure 1). 

Step 2.  Use the Trace Downstream Network Command to find all of the network below the node of interest and place it in the Doman (Figure 2).

Step 3.  Use Facility Manager to make the Lower Network in the Domain Inactive (Figure 3).

Step 4.  Change the Node of Interest from a Manhole to an Outfall

Figure 1.  Trace Upstream Network

Figure 2.  Put the lower Section of the Network in a Domain

Figure 3.  Use Facility Manager to make the Lower Network in the Domain Inactive

How to Subdivide Subcatchments in SWMM 5

Subject:   How to Subdivide Subcatchments in SWMM 5

If you want to subdivide a larger Subcatchment in SWMM 5 and get around the same peak flow then a good suggestion would be to make sure that (Figure 1):

1.   The sum of the new areas equals the original Subcatchment Area and
2.   The sum of the total Width values equals the original Subcatchment Width on the one Subcatchment
3.   The infiltration, percent imperviousness, roughness and depression storage should be the same. 

Figure 1.  Subdividing a Subcatchment

What are the Types of Force Mains (FM) in SWMM 5?

Subject:   What are the Types of Force Mains (FM) in SWMM 5?

There are five ways to model a force main in SWMM 5 for the combination of full and partial flow in the force main (Figure 1):

1.       Full Flow using Darcy-Weisbach for the friction loss

2.      Full Flow using Hazen-Williams for the friction loss

3.      Full Flow using Manning's n for the friction loss

4.      Partial Flow uses Manning's n for the friction loss for Force Main Equation options

If you use Darcy-Weisbach or Hazen-Williams then an equivalent Manning's n for a force main that results in the same normal flow value for a force main flowing full under fully turbulent conditions is calculated internally in SWMM 5 in forcemain.c

·         Equivalent n for H-W is 1.067 / Hazen-Williams Coefficient  * (Full Depth / Bed Slope) ^ 0.04 

·         Equivalent n for D-W is (Darcy-Weisbach friction factor/185) * (Full Depth) ^ 1/6 

Figure 1.  Types of Full and Partially Full Force Mains in SWMM 5

How Does a TYPE1 Pump Work in SWMM 5?

Subject:   How Does a TYPE1 Pump Work in SWMM 5?

A SWMM 5 Type1 pump is called an offline pump but the name comes from SWMM 4 and the Pump is controlled by volume instead of depth or head as in the SWMM 5 TYPE2, TYPE3 and TYPE4 Pumps.  The attached example SWMM 5 model has an offline storage node that pumps flow INTO the Offline Storage unit during high flow and FROM the Offline Storage Unit during low flow.  The SWMM 5 Real Time Control (RTC) rules determine which of the two pumps operate based on the flow in an upstream link (Figure 1). 

Figure 1.   RTC Rules and Schematic of an OffLine Pump in SWMM 5.

How is the Orifice Setting Used in SWMM 5 RTC Rules?

Subject:  How is the Orifice Setting Used in SWMM 5 RTC Rules?

The Real Time Control Rule for Orifice Setting can be a function of a Setting constant, Setting from a Curve, Setting from a PID controller and a Setting from a Time Series (Figure 1).    The Setting affects the Full Depth of the Orifice at each time step.  The setting which ranges from 0 to 1 can either completely close or open theorifice (Figure 2).   You will have to use the equivalent in ICM or else the settings derived from the SWMM 5 time series need to be multiplied by the orifice depth to have the same effect in ICM that it had in SWMM 5. 

Figure 1.  The Possibilities for defining the Setting of an Orifice in SWMM 5 from a H2OMAP SWMM RTC dialog.

 

 Figure 2.  The Setting affects the Full Depth of the Orifice at each time step.  The setting which ranges from 0 to 1 can either completely close or open the orifice.

Low Impact Development Options in H2OMAP SWMM and InfoSWMM

Subject:  Low Impact Development Options in H2OMAP SWMM and InfoSWMM

The five options are:

1.      Rain Barrel
2.      Bio Retention Cell
3.      Infiltration Trench
4.      Vegetative Swale
5.      Porous Pavement

and be entered as controls in the Hydrology Section of the Operations Browser of H2OMAP SWMM or InfoSWMM (Figure 1)

Figure 1.  The Attribute Browser Operation Tab allows you to enter LID Controls for your LID Modeling.

🌧️ Rules for NRCS Unit Hydrographs in InfoSWMM 📈

Subject: 🌧️ Rules for NRCS Unit Hydrographs in InfoSWMM 📈

When applying NRCS (Natural Resources Conservation Service) Unit Hydrographs for hydrological modeling in InfoSWMM adhere to the following rules or guidelines to ensure accurate hydrological simulations:

1. Curve Number (CN) Source 🗂️: Obtain the Curve Number (CN) from the NRCS_CN column in the Subcatchment Table, representing runoff potential based on soil type, land use, and treatment practices.

2. Time of Concentration (TC) ⏱️: The Time of Concentration, critical for hydrograph development, is sourced from the TC column within the Subcatchment Table.

3. Infiltration Model Selection 💧: Select the Infiltration Model according to the CN Infiltration Model Column in the Subcatchment Database Table to ensure consistency in infiltration calculations.

4. CN Consistency Across Tables 🔄: The CN value in the Soil Database Table must match the CN in the Subcatchment Database Table for uniform hydrological parameters.

5. Depression Storage and Initial Abstraction 🕳️➡️💧: If Depression Storage is zero in the Subcatchment Database Table, Initial Abstraction (IA) in inches will be internally calculated using the formula $��=0.2\times (1000\mathrm{/}��-10)$.

6. Initial Abstraction Calculation ✏️: Clearly state that Initial Abstraction in US units is $��=0.2\times (1000\mathrm{/}��-10)$, indicating the use of American measurement standards.

By following these emoji-highlighted guidelines 📝, hydrological modeling using NRCS Unit Hydrographs within InfoSWMM will be precise and reliable, leading to better water management outcomes. 💦🏙️

How to Export all of your Data to a Shapefile Using InfoSWMM

Subject:  How to Export all of your Data to a Shapefile Using InfoSWMM

You can do this easily by using three steps which are shown in Figure 1, Figure 2 and Figure 3.

Figure 1.  Export Manager Tool

Figure 2.  Link and Node Export Options

Figure 3. Parameter options for Export to the Shapefile

How to use the Flow Splitter in InfoSewer for Dendritic Networks

Subject:  How to use the Flow Splitter in InfoSewer for Dendritic Networks

InfoSewer, which is an extension in Arc Map, does need to have slit split defined where gravity mains merge together to determine the amount of flow in each of the downstream conduits (Figure 1).   The options for the flow splitterin each of the downstream links are:

1.       Automatic Allocation
2.       Fixed Flow Percentage
3.       Variable Flow Percentage and
4.       Inflow-Outflow Curve 

At an outfall where the invert of the outfall pipe is raised compared to the inverts of the incoming and outgoing pipes a flow split of Variable Flow Percentage or Inflow/Outflow curve may work better (Figure 2). 

Figure 1. Options for Performing a Flow Split in InfoSewer

Figure 2.  The Effect of the flow split can be used to model complex situations in a dendritic model with outfalls.

A SWMM 5 Model made from the Art of Jack Yerka

Subject:   A SWMM 5 Model made from the Art of Jack Yerka

The attached example SWMM 5 model has small rectangular conduits with a constant inflow based on a background image from Jack Yerka.

How to Save Node and Link Summary Tables in H2OMAP SWMM to Shapefiles

How to Save Node and Link Summary Tables in H2OMAP SWMM to Shapefiles

The export manager of H2OMAP SWMM is very flexible, you can export shape, MIF and CSV files but you have to do some copy and pasting to allow the program to export ALL of the node and pipe summary tables.  The export manager will export any node or pipe information in the DB hydraulic and information tables.  If you copy and paste, for example, the output pipe summary table to the Pipe information tables (Figure 1) then you can use the Export Manager (Figure 2) to save the shape file with tables(Figure 4) and view the shape file in Arc Map (Figure 4).  The TOC properties in Arc Map can be used to show the maximum d over D or maximum Q over Qfull values in Arc Map using this VBScript.

Function FindLabel ( [DOVEMAXD] )

  FindLabel = "" & FormatNumber([DOVEMAXD],2) & ""

End Function

Figure 1.  Copy and Paste the Pipe Summary information from the Output Tables to the Pipe Information  Tables.

Figure 2.  Select a link Shapefile using the Export Manager

Figure 3.  Save the Link Information and other data to a shape file.

Figure 4.  The created shapefile added to Arc Map and displayed using the Layer Properties of Arc Map