# Truncated triangular weir formula

TT1 caracterized by:

• $$C_d$$: discharge coefficient
• $$Z_d$$: triangle's lower overflow elevation
• $$Z_t$$: triangle's higher overflow elevation
• $$B/2$$: half-opening of the triangle

## Formula

### for $$Z_{am} \leq Z_t$$

$Q = C_d \frac{B}{2 (Z_t - Z_d)} \left ( Z_{am} - Z_d \right )^{2.5}$

### for $$Z_{am} > Z_t$$

$Q = C_d \frac{B}{2 (Z_t - Z_d)} \left ( \left ( Z_{am} - Z_d \right )^{2.5} - \left ( Z_{am} - Z_t \right )^{2.5} \right )$

Thin wall weir: $$C_d$$ = 1.37

Thick weir without contraction (rounded $$r > 0.1 * h1$$): $$C_d$$ = 1.27

Triangular profile weir: (1/2 upstream, 1/2 or 1/5 downstream): $$C_d$$ = 1.68 and 1.56
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