FLOOD02048

• County: Statewide
• Community: State of Colorado
• Title: Spatial Data Analysis of Nonstructual Measures - Corps - Technical Paper Number 46
• Date: 1/1/2001
• Prepared For: State of Colorado
• Prepared By: Hydrologic Engineering Center
• Floodplain - Doc Type: Educational/Technical/Reference Information

A composite damage function is defined as a stage-damage function for a
unit area for each land use category that has significant damage potential.
These functions may be developed for each land use category by averaging
the structural and related content values obtained from sampling a range
of structure values and types within each land use category by use of field
surveys. review of tax records and interviews conducted with regional and
local agencies. The composite damage function may include direct and in-
direct damages that are associated with each particular land use category.
Table 1 Composite Damage Function for Low Density Residential Land Use
Category illustrates an example of a composite stage-damage f~nction of a
land use category. These functions can be developed for other land use
categories such as pasture and develope~ open space although the corres-
ponding damages would probably be small compared to those occurring in the
structurally developed areas.

Aggregate Damage Function.--The flood damage associated with each grid
cell is determined by matching the land use for each grid cell with the
appropriate composite damage function (in effect placement of the function on
the elevation assigned to the cell). The individual cell elevation-damage
functions are then aggregated to the index location by use of the mechanism
of the reference flood. A'schematic of this procedure is shown in Fig. 3
Damage Function Development. The computer program that performs the aggr~ ,
gation may also be used in the development of the composite damage functions.
To devl!lop the composite stage-damage function for a specific land use
category, the following types of information are used. '

. stage vs % damage for structure

. stage vs % damage for contents

. value of structure

. values of contents (option. % of structure value)

o indirect damage (dollar amount or % structure and contents)

. development density (number of structure per grid cell)

. vacancy allowance (amount of land classified in the particular
category that is developed) ,

The data is prepared by land use category and the program accesses the
grid data file and computes elevation-damage relations for all pertinent
land use categories and damage reaches. Table 2 ~qqreqate Damage Functions
contains an example elevation-damage tabulation for selected land
use categories of a typical damage reach index location.

Once the damage function is developed for the land use pattern of
interest (base condition) the function can be adjusted to reflect each
specified nonstructural measure (with condition) and corresponding per-
formance criteria that are of interest in plan formulation. The cap-
ability to automatically adjust these functions is provided by the
computer program that is used to develop the aggregated damage functions.

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