Flooding affects property values

By Eng. Thushara Dissanayake

Climate change is no more a matter of controversy as there is a scientific consensus on the occurrence with predictions of horrible consequences. Further, it is no more a sheer environmental issue but ramifies into socio, economic and political spheres creating much chaos.

Sri Lanka is one of the hotspots in south Asia when climate change impacts are concerned. Although we are blessed with higher annual rainfall the developing temporal and spatial variations of the rainfall pattern cause floods and droughts. The specific geography of Sri Lanka where all rivers are flowing radially from the central hills into the flat urban terrains in the coastal belt is a favorable condition for riverine floods in the lower parts of the basins.

The rivers that are flowing on the western and southern stretch of the country or else the wet zone trigger flood events more often. Eventually, highly populated main cities like the capital Colombo, Gampaha, Kaluthara, Galle, and Matara, and their upstream suburbs always face flood risks. In addition, urban flooding is also a common problem mainly in the capital Colombo. Urban flooding is essentially caused by urbanization and lack of proper stormwater drainage facilities and intense rainfalls of short duration too, contribute a lot.

In the past cities like Colombo were affected by floods once in a while. Probably flooding was experienced by a certain generation of the public only once in their lifetime. On the contrary, those who migrated to the capital might have had no experience or knowledge of flooding when they settled in their preferred locations. Therefore, flood risk was not a big concern when deciding property values in the past as many might have seen an occurrence of flood as a rare event. Now with climate change flooding is becoming a frequent consequence which could cause colossal economic damage. It would not only affect the resident and businesses properties but also the mental health of people. Flooding is a traumatic experience when polluted water with debris devasted your property.

Flood risk on a certain land area is technically specified by the flood return period and depth of water. A 100-year return period denotes that a flood of that magnitude will occur once in 100 years though that does not mean that only one such flood will come for the 100 years or that flood will come definitely. In fact, it is an indicator of the risk. Similarly, a flood of 10-year return period would occur more frequently.

The most important parameter about flooding is the height of flood water, which increases with the return period of flood for a particular location at risk. In other words, a property at risk will get flooded to a higher depth during a 100-year return period flood when compared to that of a 10-year return period event. Perhaps, a property inundated by a 100-year flood event might not be affected by a 10-year event depending on its location. Generally, the higher the level of flood water more significant will be the cost of damage to the property. Therefore, flood risk maps are crucial to identify the nature of risk faced by a property at a particular location.

Areas commonly subjected to floods will be demarcated by such flood risk maps by the relevant authorities as an important part of flood risk management in due course. Currently, factors like the socio-economic level of the neighborhood, proximity to green areas, distance from the main city, and the like remain the location-specific factors that determine property values. However, the priorities may change from place to place based on the acquirers’ personal or business interests. Despite many aforementioned positive factors applicable to a prospective buyer scale of flood risk would be a negative factor that affects property prices. In the meantime, flood-risk-free properties in the immediate vicinity will gain value.

Knowing the flood risk and pricing the properties incorporating that would not be the end of the story. The scarcity of developable lands for residential and business purposes is a growing problem in our urban areas. Hence, it is inevitable to follow adaptive and resilient measures to prevent flood risks from becoming detrimental events or disasters. Present criteria for land clearance for development works and approval for building plans should incorporate necessary regulations, which would mitigate the flood risks, with the help of flood risk maps. Invariably such adaptive and resilient structural measures will incur additional costs. Perhaps risk transfer strategies like flood insurance would also be necessary to cover property damages and business losses due to supply chain disruptions. Further, banks and other institutions that finance developments in flood-risk areas will be more stringent about the terms of their mortgage loans. Nevertheless, a creative developer can turn these risks to his advantage by introducing novel adaptive and resilient measures which increase the value of the property.

In summary, keeping people away from flood waters is the best strategy for zero risk. Albeit, considering the high demand for lands and properties and associated socio-economic issues enforcing structural guidelines on how to live with floods could be the most pragmatic strategy. Although not discussed here properties affected by probable sea level rise too will face the same consequences and need similar adaptive and resilient measures to face the situation.

(Eng. Thushara Dissanayake is a Chartered Engineer specialising in water resources engineering with over 20 years of experience)