Taking m as the origin, MB and MP as the positive directions of X axis and Y axis respectively, a rectangular coordinate system is established.

A(-30，0)、B(30，0)、M(0，0)、P(0， 18)、A 1(-x 1， 14)、B 1(x 1， 14)、x 1 & gt； 0

The arch bridge is a parabola and the equation is y = ax 2+ 18.

Substitute A(-30,0) into the equation: 0 = A (-30) 2+ 18.

a=-0.02

Arch bridge equation: y =-0.02x 2+ 18.

Substitute A 1(-x 1, 14) into the equation:14 =-0.02 (-x1) 2+18.

x 1^2=200

x 1= 10√2

A 1B 1= 10√2×2

=20√2

≈20× 1.4 14

≈28.28

& lt30

The water is less than 30 meters.

Urgent measures are needed.