For the protection against inundation at river delta area or lowland area with developed channel systems, drainage pump stations are facilitated associated with
water gates and barrier seawalls. Many of the Japanese ports have this protection system against high surge. Sea level rise is supposed to decrease drainage speed due to the increase of the waterhead difference from the inner water surface. Global warming is also supposed to alter the pattern of rain falls and precipitation strength.
　Variety of the dimensions of drainage area, innerwater surface area and pump capacity are reviewd. Three cases of typical model area are set for the evaluation
of the effect. Increase of the water level in inner watersurface is calculated with elapsed time under a designed high surge scenario.
　Various cases are examined for the magnitude of sea level rize, precipitation strength and rain inflow time. The followings are clarified.
a) In case inside water surface area is large enough against whole drainage area, then the vulnerability for sea level rise and increase of rain fall strength becomes small.
b) Though the inside area chould be protected against inundation by means of the improved management for pumping, water gates have to be closed for longer duration because of the sea level rize.