GREEN ROOF FOR SUSTAINABLE URBAN FLOOD CONTROL VIA COST BENEFIT

GREEN ROOF FOR SUSTAINABLE URBAN FLOOD CONTROL VIA COST BENEFIT APPROACH FOR LOCAL AUTHORITY

 Project leader:

Dr. Shazmin Shareena Ab. Azis

Project members:

Dr. Muhammad Najib Bin Mohamed Razali

Dr. Nurul Hana Adi Maimum

Dr. Mohd Shahril Abdul Rahman

Dr. NurulSyakima  Mohd Yusoff

Real Estate, Faculty of Built Environment and Surveying

Universiti Teknologi Malaysia (UTM), Skudai, Johor

ABSTRACT

Global changes counting economic development, population growth, and people migration to the urban region has created densely opaque and impervious urban landscape. This is a catastrophic problem for countries receiving large and continuous annual rainfall. Impervious surface generates high storm water runoff volumes and flow rates, which overwhelm the traditional centralized drainage systems and cause frequent flash flood episodes in the urban region. Flash flood has caused tremendous damages and loss to the nation. As a result, local authority has to spend greatly to repair damages caused by this disaster. Numerous studies have proved green roof as an efficient green infrastructure in managing storm water runoff, thus, hindrance the occurrences of flash flood. However, the worth of implementing green roof for local authority remains unrevealed. Therefore, this study is conducted to assess the worth of implementing green roof for local authority using cost benefit analysis. Technically, intensive green roof performed better in reducing storm water runoff than extensive green roof at 84%. Deeper substrate and lower degree of roof slope enlarge storm water runoff reduction. Integration of intensive green roof provides 20% higher cost saving than extensive green roof for local authority. Overall, the results show that extensive green roof provides better cost benefits ratio than intensive green roof where the benefit is 1.2 to 3.5 times higher than green roof cost. Roof slope contributes the highest benefit ratio for intensive green roof at 2 times higher than minimum cost. Meanwhile, the type of vegetation provides largest benefit ratio for extensive green roof at 4.2 times larger than the minimum cost. The implementation of green roof has significantly proved to reduce the occurrences of flash flood events and also economically efficient in reducing local authority expenses for post flash flood damages. This has proved that green roof implementation is worthy for local authority as it is highly efficient for economic and environmental aspects.