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Designing Detention Pond

Pond #

Click Add in Project View to create a new MSMA project. Choose Pond, select MSMA 1st Edition, create the name of the project, and click Create. 

Pre-development #

Calculate pre-development discharge by inputting data in Pre tab. Pond design can also be integrated from drainage if the analysis of drainage has been carried out. 

  1. Input length of flow path from catchment divide to outlet, slope of stream flow path and catchment area to obtain tc and it is editable.
  1. Select location. 2P24 and FD are generated automatically. Both are editable when tc less than 30 minutes.
  1. Select Minor and Major Design ARI.
  1. Click the “ Calculate” button to obtain Minor and Major Storm discharges.

Post-development #

Calculate post-development discharge by inputting data in the Post tab.

  1. Input overland sheet flow path length, slope of overland surface and manning coefficient to obtain to.
  1. Input drain flow length and average velocity to obtain tp.
  1. Input total catchment and define the sub-catchments for pervious and impervious areas.
  1. Click the “ Calculate” button to obtain post-development critical storm duration.

Pond Sizing #

Determine required storage by inputting data in the Pond Sizing tab. Pond sizing design can be synchronized with Pond Platform. Pond platform can be assigned in EW modules (Platform > Spread Input > Type Column > Assign the platform as Pond).

  1. Choose Pond Type.
  2. Input the dimension of the pond design.  
  3. The graphical pond displayed can be rotated to different views.
  4. Click the “ Calculate” button to obtain the volume and pond top area.

Outlet Design #

Design the outlet by inputting data in the Outlet Design tab.

  1. Design Storm Primary Outlet

a. Input orifice height between pond and orifice invert level, H.

b. Select Orifice Type.

c. Input orifice diameter, Do and number of orifice.

d. Click “ Routing” to obtain “Maximum Water Level”.

e. Post-development storm outlet maximum discharge must be lower than pre-development minor design storm peak flow.

  1.   Major Design Storm Primary Outlet

a. Major storm primary outlet design is optional. Untick the box to exclude major design storm primary outlets.

b. Input orifice height between pond and orifice invert level, H. H for Major Design must be higher than “Maximum Water Level of Minor Design – Pond Invert Level”.

c. Select orifice type. 

d. Input orifice diameter, Do and number of orifice.

e. Click “ Routing” to obtain “Maximum Water Level”

f. Post-development major design storm outlet maximum discharge must be lower than pre-development major design storm peak flow.

  1.   Secondary Outlet Arrangement

a. Input weir height between pond and spillway invert level, H. H for Secondary outlet must be higher than “Maximum Water Level of Major Design – Pond Invert Level”.

b. Input weir width.

c. Select ARI.

d. Click “ Routing” to obtain “Maximum Water Level”.

Note: “Input is not completed” message pops out if the Routing button is not clicked. Therefore, the Routing tab must be clicked before analyzing. The message is as below. 

Result #

Click the “ Analyse” button to generate the results.

Water Level Simulation will be shown for every 5 minutes interval.

Click Textual Report, Summary Report, Graph, or Water Level Profile tabs to show the outcomes respectively.

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