# Protective Structures

These structures are designed to minimize damage to other irrigation structures especially during extreme conditions.

# Drainage Structure

Drainage 1

Drainage 2

Vertical Drop

Vertical Drop

Vertical Drop Section

Below are the most commonly used type of spillways.

Straight Drop Spillway

Pantabangan Spillway

Pantabangan Spillway

Chute Spillway

Side Channel Spillway

Mornig Glory

Flower

$\Large x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$

where:

Q = discharge capacity of the weir

H = available head

C_d = weir constant

Transitions are intermediate structures constructed when connecting either two (2) channels of different section or when connecting a channel to a canal structure.
Most transitions that are interfacing different types of materials (e.g. concrete and earth) are equiped with cut-off-walls. This is to minimize the creep of water under the structure.

Transition 1

Transition in a regulating structure

Transition 2

Transition in an inverted siphon inlet

Cut-offs are constructed as part of a larger structure
They are used to prolong the travel of seepage creep under a structure minimizing or eliminating the potential damage that it may cause.

Cut Off Wall

Stilling Pool

Stilling pool at Panan-Dalayap Diversion Dam

NLIP Dam

They help dissipate energy of the water, thus reducing the required length of the downstream apron or stilling pool.