FLOOD02020

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Title: Feasibility Evaluation Multijurisdictional Urban Drainage Projects
• Date: 2/1/1977
• Prepared For: UDFCD
• Prepared By: Multiple Authors
• Floodplain - Doc Type: Educational/Technical/Reference Information

49

residential area. Damages for the other depths would be determined

in a similar ~anner. The data can also be presented graphically as

in Figure A-2.

For areas that are not homogeneous with respect to land use or

damage potential, a more detailed analysis must be performed. For

each land use category the value of property exposed to flooding must

be known. The exposure is multiplied by the damage factor taken from

an appropriate depth versus damage curve. Dollar damage is estimated

and tabulated for each damage category, as in Table A-4.

Available depth versus damage tables reflect flood damage due to

standing water. In addition, there is a potential for damage due to

the velocity of the flood water. Erosion and structural damage due

to undermining and flotation are possible if the velocities are signi-

ficant. Data for estimating this type of damage are not readily avail-

able. It is recommended that at lE~ast the velocity head be added to

the flood depth when velocities exceed 8 fps, to account for some of

the damage that might occur. The depth-damage relationships previously

presented account somewhat for the velocity phenomena by predi ct ing

100 damage at some depths.

C. Compute Base Line Average Annual Damages

Total the flood damages for each reach and recurrence interval

as shown in Table A-5 for one reach.

For each reach, construct a graph of flood damage versus probability

of exceedance In any given year. The graph will be similar to Figure

A-3. Since the rarest flood calculated may be the 1 event (lOO-year),

the 0 event must be estimated and plotted. It can be estimated from the

slope at the end of the curve. The zero damage point must also be