# Spinifex

This Burrows (2018) rate of spread model was developed for predicting fire spread rates in hummock spinifex grasslands.

### Vegetation

Hummock spinifex grasslands

### Fuel inputs

moisture
cover
• Compound fuel moisture content (%)
• Spinifex ground coverage (%)

### Code

```// Hummock spinifex grasslands
// Burrows (2018)

// -------------------------------------------
// Model parameters
// 1. Spinifex clump profile (mean) moisture content (% oven dry weight), 'm' (input)
// 2. Fuel cover (live and dead spinifex and other vegetation <1.5m high) (%), 'cover' (input)
// -------------------------------------------

// Backing and flanking coefficients compared to head fire ROS
REAL wind_speed = length(wind_vector);

// Calculate length-to-breadth ratio (LBR) for grassland
REAL LBR = 1.0;
if (wind_speed < 5){
LBR = 1.0;
} else {
LBR = 1.1*pow(wind_speed, 0.464);
}

// Determine coefficient for flank rank of spread
REAL cc = sqrt(1.0-pow(LBR, -2.0));
REAL cb = (1.0-cc)/(1.0+cc);
REAL a_LBR = 0.5*(cb+1.0);
REAL cf = a_LBR/LBR;

// Determine shape parameters
REAL f = 0.5*(1.0+cb);
REAL g = 0.5*(1.0-cb);
REAL h = cf;

// Now calculate a speed coefficient using normal flow formula
REAL speed_fraction = (g*wdot+sqrt(h*h+(f*f-h*h)*wdot*wdot));

REAL SI = 0.305*wind_speed + 0.311*cover - 0.676*m - 4.073;
REAL wind_speed_e = wind_speed / 1.35; // Eye level wind speed
if (SI > 0) {

// Calculate speed
head_speed = 40.982 * pow(wind_speed_e,1.399) * pow(cover,1.201) / pow(m,1.699);

// Convert from m/h to m/s