While the recent flood may seem like one of the worst in modern history, it is certainly not the first. The Rakyat Post, in its recent article provides a simple chronology of 3 great flooding events in Malaysia which seems to happen every 50 years or so, with one of the first recorded in 1926 and the last disaster in 1971. And apart from 50 year flood events, most of the recently affected areas in Shah Alam and Klang have been plagued with annual sometimes knee-high floods that usually go unnoticed by the media. So, one would think that by now the government would have enforced ample mitigation strategies to prevent the devastating damage caused by floods.
The short answer is, they have, and it failed.
Some large-scale mitigation efforts in accordance with the Klang River Basin Environmental Improvement and Flood Mitigation Project implemented by the Department of Irrigation and Drainage (DID) include construction of the SMART tunnel, introduction of the Paya Indah wetlands, adaptation of MASMA principles in town planning and river improvement projects, and on a smaller scale introduction of flood gates and pumps in key flooding neighborhoods.
Some may argue that the reason of this failure is due to the unforeseen volume of rainfall and unanticipated high tides which caused inability for river waters to flow into the sea. But there are numerous strategies that could have prevented the floods in many areas and significantly reduced the destruction caused by it.
As designers, engineers and developers, we have a responsibility in ensuring these strategies are explored and where feasible and necessary, implemented accordingly.
We'll explore some necessary steps that could prevent the scale of destruction caused by a forecasted flood event (be it a 5-year or 100-year event) in this article.
Availability of a Flood Risk Assessment or Flood Plain Report
Heavy rainfall and unpredictable patterns of rain events are going to become more prevalent as we experience the ever-developing effects of Climate Change, the IPCC report has alerted South East Asia on the intensifying of rainfall events by up to 7% for every degree of global warming. The dangers of heavy rainfall is not limited to damage caused by floods but also disastrous landslides that could severely destroy properties and infrastructure and threaten lives.
So how are these risks assessed in a new development? Let’s take a quick look at the procedure…
In approving a stormwater management plan for a new development, the developers and project design teams are typically required to submit documentation including design drawings and calculation reports showing compliance to the Urban Stormwater Management Manual for Malaysia (MSMA).
The MSMA guideline is a comprehensive document which provides stormwater best management practices such as design of permeable pavements, bioretention areas, vegetated swales and other Sustainable Drainage (SuDS) recommendations for control of run off quantity AND quality. However, the guideline is not always referenced in its entirety by engineers, but rather only for elements that require authority submission, this is typically limited to stormwater quantity control by means of detention tanks, and rainwater harvesting systems. Other elements such as ecological plants for bioretention systems, and gross pollutant traps to maintain quality of stormwater run off are often overlooked.
In designing for climate resilience, it is crucial to study and understand the exact nature of the site that is being built on and how it impacts its surrounding environments. The BREEAM Green Building rating tool, and other green building rating tools address this by requiring projects to submit a Flood Risk Assessment (FRA). An FRA would inform developers and the approving body of the possible risks associated with the development and strategies that must be enforced to avoid severe damage caused by flood.
To our knowledge, a flood risk assessment is currently not an authority approval requirement under any local council in Malaysia. In fact, in our experience, attaining flood plain reports and zoning from relevant departments is also not an easy feat.
Preparing an FRA would allow designers to categorize a development as either “Low Risk”, “Medium" or "High Risk” zones. This report can then inform design decisions made for these developments. This would include determination of the platform level of the building (being designed above the design flood level), implementation of appropriated SuDS features and stormwater BMPs as well as M&E system design to reduce damage from flooding.
To effectively implement the MSMA guidelines for project specific scenarios, all local councils should introduce requirements for a mandatory Flood Risk Assessment (FRA) especially for low-lying areas, and depending on the assessed risk level of the site, enforce stricter requirements for implementation of flood prevention strategies.
Preparation of an FRA would force engineers to investigate the history of the location and risks associated with compensating flood mitigation efforts for low-cost alternatives and will also create an awareness on the impact of the development on neighboring existing townships.
Along with the Environmental Impact Assessment (EIA) and Social Impact Assessment (SIA), an FRA should inform design decisions and not merely act as an authority submission requirement with no actionable outcome.
Strategies to Reduce Probability and Severity of Flood
As designers, town planners and engineers, we need to acknowledge that our designs are always susceptible to the wrath of nature at any given time. We need to prepare for this and build WITH the elements as much as we build to protect AGAINST the elements.
Building flood gates and dikes and pumps to redirect flood water is very necessary, but simply insufficient. Rainfall will always be a part of our existence and it will only get heavier with climate change. Traditional kampung houses built on stilts acknowledged this but with the speed and scale of buildings in modern times, it is easy to forget and difficult to replicate.
A climate resilient design would allow water to flow through its grounds and not restrict the movement of water. This means, lower levels should not be built as occupiable spaces but rather as either pervious grounds for infiltration or flexible spaces such as carparks that can be converted into drainage facilities during heavy rains, as is the case for the SMART Tunnel.
Parks and public areas within projects can be converted to impervious grounds that transform into retention ponds during heavy rainfall events. To cater to this, minimum site area for open vegetated space within any new flood prone development should be MORE than the typical requirement of only 10%.
Incorporating design of road drainage vegetated swales in place of concrete drains to provide a form of bioretention must be implemented on a larger scale to accommodate large stormwater run offs.
Building Facilities That Reduce Impact of Floods
Designing a climate resilient building does not end in mitigation measures. Adapting to the possibility of severe flooding is part of a holistically climate resilient building.
An important element to having a successful flood adaptation plan is to have in place an early warning system. With a reliable system in place, residents could have been evacuated, properties such as cars and other electronics could have been moved to safety and most importantly, lives could have been spared.
With proper reporting of flood plains, designated elevated shelters can be constructed within identified high-risk areas to allow quick evacuation of residents and vehicles in the case of unanticipated floods or flash floods. These designated shelters could serve as non-permanently occupied, public spaces during non-flooding periods and should be equipped with basic necessities for occupants during these emergencies.
Part of adaptation also looks at the selection of materials in building design. In Netherlands, a multi-safety level approach to flood management is taken which comprises of prevention, sustainable spatial planning and disaster management. Under disaster management, water-robust construction is applied whereby building in flood plains can be sealed off by means of waterproof partitions or retaining walls, contain hatches, building are built on raised ground or even designed to float.
Read more about the Netherlands flood management plan here
Aside from the big ticket disaster management strategies, minor improvements in home designs can also be implemented. In larger buildings, mechanical systems should not be placed at basement levels but rather on higher levels to prevent damage, electricity disturbances and fires during flooding events, and in homes, wall switches should be placed at least 1.5 meters from the floor in anticipation of flood.
Protecting Flood Affected Communities is Our Responsibility
The recent floods saw amazing numbers of volunteers flock to aid flood victims by various means, be it donations, cleanup assistance, rescue missions and the likes. However, our responsibility to the flood victims does not end when a 50-year flood event ends. It is a long-term commitment as members of society living in an era where climate change is accelerating at unprecedented rates.
As designers, engineers and general public, we have a responsibility to remember the 2021 flood event in our day-to-day actions, be it in sizing a stormwater detention tank, introducing greenery in place of impervious surfaces, or even littering into a drain that leads to the river which overflows into our cities during heavy rainfall.