Is There a Limit to Detention/ Retention Pond Area?

When it comes to designing detention and retention ponds in Malaysia, one question often raised is whether the pond area must not exceed a certain percentage of the catchment or development area. Here’s a breakdown of the relevant guidelines and common practices adopted across Malaysia to help clarify this.

 MiTS Key Design References: MSMA 2.0 and SuSTOM #

In MiTS, our detention facility design refers to the following guidelines:

1. MSMA 2.0 (Urban Stormwater Management Manual for Malaysia)
2. SuSTOM (Sarawak Urban Stormwater Management Guideline)

These two references form the backbone of stormwater design in both Peninsular Malaysia and Sarawak. Let’s look into how each guidelines addresses detention pond sizing.

What Does SuSTOM Say? #

SuSTOM provides clear guidance on detention/retention pond sizing in Sarawak. It states that the pond area shall occupy 3% to 5% of the project development area. This guideline is relatively straightforward and often used as the primary sizing baseline in Sarawak-based projects.

What About MSMA 2.0? #

While MSMA 2.0 does not prescribe a specific percentage for detention/ retention pond area, many consultants and local councils in Peninsular Malaysia will use rule of thumb as a preliminary pond grading estimation before refining with actual calculations. 

Below are common practices that engineers follow:

CRITERIA	TYPICAL/ RECOMMENDED RANGE
Pond Area	Minimum 5% of the development area to be reserved
Pond Depth	1.5m to 3.0m (Common range for safety and maintenance access)
Freeboard	Embankment level must be at least 300mm above the pond level during emergency spillway operation.
Side Slopes	1V:4H for safety, sometimes 1V:3H if space is limited

 

These rule of thumb are commonly based on:

1. Accumulated experience from past approved submissions.
2. Frequently seen in local design reports, usually in early-stage infra plans.
3. Sometimes reflected in Pihak Berkuasa Tempatan (PBT) submission checklists, although not always officially documented.

Even though MSMA does not give a specific percentage of pond area, it emphasizes that post-development peak discharge (Q_post) should not exceed pre-development peak discharge (Q_pre) as stated in MSMA 2.0 – Chapter 1. Therefore, designers are encouraged to use hydrological analyses to determine appropriate storage volumes and pond dimensions.

Practical Implementation: What Do Authorities Require? #

In the absence of a definitive guideline on pond sizing for Peninsular Malaysia, certain local authorities impose their own guideline. For example:

1. JPS Malaysia (DID) uggests a minimum of 3% of the project area to be reserved for detention/retention facilities.

2. DBKL (Kuala Lumpur City Hall) has released Garis Panduan Jalan dan Perparitan, GPJP (Pindaan 2023) .

Under this guideline, the required pond area for detention/ retention pond in developments within DBKL’s jurisdiction shall comply with the specified standards outlined below.

Thus, while SuSTOM gives a 3% to 5% range, local authorities may have varying requirements based on jurisdiction.

Handling Constraints in Project Design #

In projects where land is constrained, it may not be feasible to adhere strictly to these percentages. In such cases:

1. The design should be backed by hydrological and hydraulic analysis.
2. Engineers may negotiate with local authorities to justify alternative designs based on Qpost ≤ Qpre compliance.

The most critical requirement is to ensure Qpost ≤ Qpre, regardless of pond size percentage. Flexibility exists, but solid engineering reasoning and proper documentation are essential.

How MiTS Handles This #

In the absence of a definitive guideline on pond sizing for Peninsular Malaysia, MiTS adopts the convention as 3~5%. Users may change the pond area sizing to align with project-specific constraints or local authority requirements.

Conclusion: Is 5% a Hard Limit? #

No, it is not. 5% is not a strict upper limit. It’s a guideline range often used for estimation purposes in our MiTS software. The key requirement is ensuring that the detention facility can manage stormwater effectively and that Post-development flows must not exceed pre-development levels (Qpost ≤ Qpre).

Upon discussion with the local authorities, you may make the pond area can be less or more than 5%, depending on site and design conditions.