Flooding - Past Hazard Events, Risk and Potential Damage   Floods are relatively less frequent in occurrence in Boundary County than other hazards, but historically, ravine flooding and ice jam floods have been the most serious, devastating, and costly hazards to affect Boundary County of all the various hazards occurring during the period of analysis. 

The steep, mountainous terrain in the county creates a flood-prone environment and development is often confined to areas adjacent to stream channels.  The Kootenai River has historically flooded its valley.  Significant events and disasters have occurred, particularly to the City of Bonners Ferry.  A review of newspaper records indicates that significant flood events occurred in 1933, 1934, 1948, 1957, 1964, and 1972.

In the past, the Kootenai River routinely crested its banks and flooded the downtown section of Bonners Ferry.  The river also frequently flooded farm ground along the riverbanks.  Bonners Ferry gained notoriety for enduring heavy floods during the 1920's through the 1960's.  The completion of the Libby Dam in the early 1970's eliminated almost all flood threat to the city from normal high runoff events. 

There is considerable debate, however, over river levels that cause extensive damage to agricultural interests along the river.  The U.S. Fish and Wildlife Service wants to maintain flows of 1,772 feet in elevation through releases from Libby Dam during certain periods for sturgeon and burbot fish populations.  The National Weather Service and Corps of Engineers has defined 1,764 feet MSL at the Bonners Ferry Bridge as flood stage, and the agricultural community has experienced significant damages when river levels higher than 1,758 feet MSL have occurred due to high flows during runoff or when high levels were maintained for threatened and endangered species. 

Many Boundary County residents live near the Kootenai and Moyie Rivers or along creeks.  As the county population has grown and moved to more rural areas, flooding of side streams in high flow events have caused significant property damage from time to time.  Floods in Boundary County primarily damage roads, structures, and some farmlands, leading to disruption of lives and business.  Flooding, in conjunction with landslide events, has contributed to road damage so severe that transportation routes have been cut off and people have been isolated for a period of time or severely inconvenienced because they have had to take longer transportation routes until the road is repaired.

In February 1996, Boundary County commissioners declared an emergency and Disaster Services requested an emergency incident designation for a spring run-off flood event.  There had been a heavy snow fall during the winter of 1995/1996.  Old roadways with little to no ballast in the road structure were later determined to be a factor in the damage caused by this event.

A large ice dam was reported on Moyie River near East Port.  With assistance from the military, engineers were able to assess the hazard from the air.  The dam was determined not to be a high risk and was left to break up naturally.   One residence was evacuated and no damage was recorded.

According to the County Emergency Incident Command records, several county roads were affected but only a few homeowners were asked to evacuate. 

   Local fire districts assisted in sandbagging Trail Creek Road near Highway 95.  This roadway was closed until it was cleared.  Other areas were affected but no details were documented.  First Interstate Bank agreed to loan Boundary County $100,000.00 for immediate road repairs.

Table 7-1.  Historical Records of Flooding Events in Boundary County

Date                                         Notes                                       Effects

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