Emergency management plan for coastal flooding risks and mitigation strategies

Management

In this presentation, I would introduce the two main types of flooding associated with hurricanes -- coastal flooding and flash flooding. I would explain what each of these flooding types is, how they are created, what types of damage they are capable of, and how they can either be prevented or the impacts ameliorated.

Coastal flooding is associated with a storm surge, a condition that arises when a hurricane or tropical storm results in higher than normal tidal action. Coastal flooding from storm surge was the primary cause of devastation associated with Hurricane Katrina, and has the potential for devastation. The damage from coastal flooding typically is on lowland areas, so the potential for damage to our town from coastal flooding is in part dependent on geography (NRC, 1994). In the presentation I would show a map of our region, highlighting the areas according to their coastal flooding risk.

The most common defense against coastal flooding is structural, in the form of dykes and levees, locks, reservoirs and other such defenses intended to contain excess water and keep it out of low-lying areas. The presentation will outline the strength of these defenses in our area, based on the understanding that storm surge can exceed fifteen feet of height, and based on the age and expected structural integrity of our region's current defenses. A computer model will be used to illustrate the ability of our system to handle storms of a variety of different strengths, up to Category 5. Such models, including MIKE 11 and HEC-UNET, will augment the presentation by providing a clear visual picture of the types of damage that can be expected with hurricane-associated coastal flooding (Chowdhury & Kjelds, 2002).

Flash flooding is associated with severe rainfall, and can occur with a hurricane or tropical storm. The natural and man-made drainage systems are inundated with water beyond their capacity. These types of floods can arise quickly and can be particularly dangerous. FEMA (2010) characterizes flash floods as a "dangerous wall of roaring water that carries rocks, sticks, mud and other debris and can sweep away most things in its path." That such floods can arise without warning, and even without rain in the area, makes them especially dangerous. As flash floods typically occur along rivers, streams or in low-lying areas, the presentation will outline some of the major flash flood threat areas in our region. Estimates of potential damage will be given, based on the density of buildings, property and people in the potentially affected areas. The patterns of flash floods are less predictable and there is little advanced warning, which means that most flash flood management strategies are preventative in nature (i.e. keeping houses out of the most threatened areas).