The role of mangroves in attenuating storm surges

Effects of different management regimes on mangrove ecosystem services in Java, Indonesia

“…Government regulation No.32 (1990) sets a minimum width of 200 meters for mangrove greenbelts along the coastline and 50 meters along riverbanks. Although mangrove forests are generally found on shores with relatively low incoming wave energy, research has shown that larger waves and even elevated water levels as a result of storm surges and tsunamis can be received by mangrove areas (Mazda et al 2006, Zhang et al 2012. Mangroves can reduce wave energy and height, hamper the inland movement of storm surges, and reduce coastal abrasion, mainly because of their root structure and strength and if a sufficiently large area of mangroves is present ( Figure 3).…”

“…Mangrove plantations have fewer openings in their projected areas, due to the absence of ponds and gutters (Zhang et al 2012). In fact, many mangrove plantations in Indonesia have been created specifically for their coastal protection potential (Bosire et al 2008).…”

“…The main difference with wave attenuation is that storm surges cannot be assigned linear relationship to any of these factors. Mangrove width, for instance, has generally been related to storm surge reduction in a simplified, linear manner, but these results must be treated with caution as the largest reduction in peak water levels generally occurs at the seaward edge of the mangroves, while further inland the water level can change more slowly (Zhang et al 2012). …”

“…Characteristics that influence the ability of mangroves to reduce storm surge levels can be assumed to be quite similar to those mentioned above (wave attenuation), albeit with less certainty. Mangrove width, vegetation characteristics (roots, stems, branches) and topography have been mentioned as the major factors (Mazda et al 1997a, Quartel et al 2007, Zhang et al 2012). The main difference with wave attenuation is that storm surges cannot be assigned linear relationship to any of these factors.…”

“…This implies that a mangrove belt several kilometres wide is needed to significantly reduce storm surge water levels. It has to be noted that, unlike wave attenuation, this reduction is non-linear over distance travelled by the surge (Zhang et al 2012). Because of high diversity, age, density of roots, stems and branches and related factors, it can be assumed that storm surges can be reduced almost entirely, provided that the width of the mangrove area is sufficient and that the presence of rivers and open areas does not reduce the ability of mangroves to reduce peak water levels (Krauss et al 2009, Zhang et al 2012).…”