44
a factor of 2 within 50 metres of the front of the mangrove forest. Hence, the wave
heights are typically attenuated by a factor of square root 2 given that the wave
energy is related to the square of the wave height. Both field and model results also
indicated that longer period waves, such as swell waves, are subjected to less attenuation, while short period waves with frequencies typical of locally generated wind
waves lose substantial energy due to interactions with the vegetation.
Badola and Hussain (2005a,b) evaluated the protective function of mangroves of
Bhitarkanika in the maritime state of Orissa, India. The Bhitarkanika mangrove
ecosystem is the second largest mangrove forest of mainland India (Fig.  2.4).
Originally around 672 km
2
, it is now limited to an area of 145 km
2
and is a wildlife
sanctuary. This mangrove forest and the associated coastal belt sustain a rich diversity of Indian mangrove flora and fauna. The mangrove forests of Bhitarkanika
Fig. 2.4 Experimental sites at Orissa to evaluate the defensive role of mangroves against cyclone
2 Mangroves: A Shield Against Storms and Wave Actions