**2. Study area**

Assam State, situated at the north-east of India and foothills of the eastern Himalayas, covers an area of 78,438 sq. km and lies in the middle reach of the Brahmaputra River and Barak (http://www.asbb.gov.in/geophysical.html). The state is bounded by 88.25°E to 96.00°E longitude and 24.50o N to 28.00o N latitude (**Figure 1**). Mean annual temperature varies from 6–38°C and average annual rainfall is 3000 mm on the Brahmaputra River valley and the surrounding region. In Assam State around 51 types of forests and sub-forests can be found. Physiographically the state can be classified into 3 groups, viz. vast alluvial plains of the Brahmaputra River valley in the north, the central Assam hills and the hilly and alluvial terrain in the south.

In the present study, the ecological disturbance regime of the Assam forest area, India has been analyzed. Based on the intensity of flood and fire incidence, total 16 forests have been selected for MGDI based thresholds development and

*Assessment of Ecological Disturbance Caused by Flood and Fire in Assam Forests, India… DOI: http://dx.doi.org/10.5772/intechopen.94282*

#### **Figure 1.**

*(a) Location of the study area in India (b) flood and fire prone forests.*

discrimination of the disturbed areas. The details of the selected forests, i.e. eight for each of flood and forest fire, were shown in **Figure 1**. The flood prone forests were mainly situated along the Brahmaputra River, whereas the fire prone forests were distributed throughout the Assam State.

### **3. Data used**

#### **3.1 Satellite data**

The 16-day composite Enhanced Vegetation Index (EVI) data products (MOD13Q1) and 8-day composite Land Surface Temperature (LST) data products (MOD11A2) for the period of 2001 to 2011 were downloaded from the MODIS web-site (www.e4ftl01.cr.usgs.gov/MOLT/). The datasets were re-projected to Geographic (Lat/Long) projection and respective scale factors were applied on the datasets [16]. The 8-day composite LST data was converted to 16-day composite using simple average, as the EVI is available at 16-day interval.
